site:
If you include [site:] in your query, Google will restrict the results to those websites in the given domain. For instance, [help site:www.google.com] will find pages about help within www.google.com. [help site:com] will find pages about help within .com URLs. Note there can be no space between the "site:" and the domain.
allintitle:
If you start a query with [allintitle:], Google will restrict the results to those with all of the query words in the title. For instance, [allintitle: google search] will return only documents that have both "google" and "search" in the title.
intitle:
If you include [intitle:] in your query, Google will restrict the results to documents containing that word in the title. For instance, [intitle:google search] will return documents that mention the word "google" in their title, and mention the word "search" anywhere in the document (title or no). Note there can be no space between the "intitle:" and the following word. Putting [intitle:] in front of every word in your query is equivalent to putting [allintitle:] at the front of your query: [intitle:google intitle:search] is the same as [allintitle: google search].
allinURL:
If you start a query with [allinURL:], Google will restrict the results to those with all of the query words in the URL. For instance, [allinURL: google search] will return only documents that have both "google" and "search" in the URL. Note that [allinURL:] works on words, not URL components. In particular, it ignores punctuation. Thus, [allinURL: foo/bar] will restrict the results to page with the words "foo" and "bar" in the URL, but won't require that they be separated by a slash within that URL, that they be adjacent, or that they be in that particular word order. There is currently no way to enforce these constraints.
inURL:
If you include [inURL:] in your query, Google will restrict the results to documents containing that word in the URL. For instance, [inURL:google search] will return documents that mention the word "google" in their URL, and mention the word "search" anywhere in the document (URL or no). Note there can be no space between the "inURL:" and the following word.
cache:
The query [cache:] will show the version of the web page that Google has in its cache. For instance, [cache:www.google.com] will show Google's cache of the Google homepage. Note there can be no space between the "cache:" and the web page URL. If you include other words in the query, Google will highlight those words within the cached document. For instance, [cache:www.google.com web] will show the cached content with the word "web" highlighted.
link:
The query [link:] will list webpages that have links to the specified webpage. For instance, [link:www.google.com] will list webpages that have links pointing to the Google homepage. Note there can be no space between the "link:" and the web page URL.
related:
The query [related:] will list web pages that are "similar" to a specified web page. For instance, [related:www.google.com] will list web pages that are similar to the Google homepage. Note there can be no space between the "related:" and the web page URL.
info:
The query [info:] will present some information that Google has about that web page. For instance, [info:www.google.com] will show information about the Google homepage. Note there can be no space between the "info:" and the web page URL.
define:
By using the Google command, define: and then a word or phrase such as "hospital", for instance [define: hospital], will return a definition or a group of definitions from various online websites, portals and online encyclopedias.
quotation marks
You maybe searching for a web page where an exact phrase is mentioned. By using quotation marks such as, ["search engines"], will bring back pages that only mention the phrase search engines in this exact form. The order of the results is still determined by the Google algorithm.
common words, letters or numbers
Google tends to ignore common words and characters such as "where" and "how", as well as certain single digits and single letters. Google will inform you if a common word has been excluded.
If a common word is essential to getting the results you want, you can include it by putting a + sign in front of it. (Be sure to include a space before the + sign.)
Negative words
If your search term has more than one meaning (bowl, for example, could refer to a cerial bowl or the bowling alley) you can focus your search by putting a minus sign (-) in front of words related to the meaning you want to avoid.
For example, bowl -cereal would take out mentions of cereal bowls in the results.
calculator
To use Google's built-in calculator function, simply enter the full sum you'd like done into the search box and hit the enter key. The calculator can solve math problems involving basic arithmetic, more complicated math, units of measure and conversions, and physical constants. To use this feature there is no special command!
Source
If you include [site:] in your query, Google will restrict the results to those websites in the given domain. For instance, [help site:www.google.com] will find pages about help within www.google.com. [help site:com] will find pages about help within .com URLs. Note there can be no space between the "site:" and the domain.
allintitle:
If you start a query with [allintitle:], Google will restrict the results to those with all of the query words in the title. For instance, [allintitle: google search] will return only documents that have both "google" and "search" in the title.
intitle:
If you include [intitle:] in your query, Google will restrict the results to documents containing that word in the title. For instance, [intitle:google search] will return documents that mention the word "google" in their title, and mention the word "search" anywhere in the document (title or no). Note there can be no space between the "intitle:" and the following word. Putting [intitle:] in front of every word in your query is equivalent to putting [allintitle:] at the front of your query: [intitle:google intitle:search] is the same as [allintitle: google search].
allinURL:
If you start a query with [allinURL:], Google will restrict the results to those with all of the query words in the URL. For instance, [allinURL: google search] will return only documents that have both "google" and "search" in the URL. Note that [allinURL:] works on words, not URL components. In particular, it ignores punctuation. Thus, [allinURL: foo/bar] will restrict the results to page with the words "foo" and "bar" in the URL, but won't require that they be separated by a slash within that URL, that they be adjacent, or that they be in that particular word order. There is currently no way to enforce these constraints.
inURL:
If you include [inURL:] in your query, Google will restrict the results to documents containing that word in the URL. For instance, [inURL:google search] will return documents that mention the word "google" in their URL, and mention the word "search" anywhere in the document (URL or no). Note there can be no space between the "inURL:" and the following word.
cache:
The query [cache:] will show the version of the web page that Google has in its cache. For instance, [cache:www.google.com] will show Google's cache of the Google homepage. Note there can be no space between the "cache:" and the web page URL. If you include other words in the query, Google will highlight those words within the cached document. For instance, [cache:www.google.com web] will show the cached content with the word "web" highlighted.
link:
The query [link:] will list webpages that have links to the specified webpage. For instance, [link:www.google.com] will list webpages that have links pointing to the Google homepage. Note there can be no space between the "link:" and the web page URL.
related:
The query [related:] will list web pages that are "similar" to a specified web page. For instance, [related:www.google.com] will list web pages that are similar to the Google homepage. Note there can be no space between the "related:" and the web page URL.
info:
The query [info:] will present some information that Google has about that web page. For instance, [info:www.google.com] will show information about the Google homepage. Note there can be no space between the "info:" and the web page URL.
define:
By using the Google command, define: and then a word or phrase such as "hospital", for instance [define: hospital], will return a definition or a group of definitions from various online websites, portals and online encyclopedias.
quotation marks
You maybe searching for a web page where an exact phrase is mentioned. By using quotation marks such as, ["search engines"], will bring back pages that only mention the phrase search engines in this exact form. The order of the results is still determined by the Google algorithm.
common words, letters or numbers
Google tends to ignore common words and characters such as "where" and "how", as well as certain single digits and single letters. Google will inform you if a common word has been excluded.
If a common word is essential to getting the results you want, you can include it by putting a + sign in front of it. (Be sure to include a space before the + sign.)
Negative words
If your search term has more than one meaning (bowl, for example, could refer to a cerial bowl or the bowling alley) you can focus your search by putting a minus sign (-) in front of words related to the meaning you want to avoid.
For example, bowl -cereal would take out mentions of cereal bowls in the results.
calculator
To use Google's built-in calculator function, simply enter the full sum you'd like done into the search box and hit the enter key. The calculator can solve math problems involving basic arithmetic, more complicated math, units of measure and conversions, and physical constants. To use this feature there is no special command!
Source