Stop words

Google ignores "and", "the", "where", "how", "what", "or" (in lowercase), and other similar words along with certain single digits and other characters.

These words are used very often and carry very little meaning. Not ignoring them would slow down the system unnecessarily.

They are called 'stop words'.

If you want a stop word included in your query, you can use the + operator, or enclose a phrase with a stop word within quotation marks.

Word order

The order of keywords in a Google query matters. Google considers the first keyword as the most important, the second keyword the second most important, and so on.

Boolean search operators

• AND. By default, Google returns pages that include all of the keywords in your query. It is equivalent to Boolean AND. In some cases, as with stop words, the + operator can play the role of AND.
• OR. Either the word OR in uppercase letters or the pipe symbol '|' instructs Google to return pages with any one or more keywords in a query.
• NOT. The Boolean NOT operator excludes a word from a search. Google uses the '-' operator for the purpose.
• Combining operators. Google reads the query from left to right. For example,
  canon EOS 300D manual OR guide filetype:pdf
  reads,"Locate all pages that have 'canon', 'EOS', and '300D' anywhere in the document, as well as 'manual' or 'guide', or both. From those pages, select documents that are PDF files."

Wildcards

A wildcard character is a special character that represents one or more other characters. The most commonly used wildcard characters are the asterisk (*), which typically represents zero or more characters in a string of characters, and the questionmark (?), which typically represents any one character. (Whatis.com)

Google has an asterisk '*' for a wildcard. It matches one or more entire words. For instance, "driving * pasadena" match both "driving to pasadena" and "driving all the way down to pasadena", as well as other hits.

Limitations

Google has its limits.

• Google may index only part of a web page. The rest of the page would be missing from search.
• Google limits searches to 32 terms. This includes keywords as well as advanced operators, but not wildcards.

Cached pages

As Google crawls the web, it makes copies of web pages. When you do a search, it is these stored, or 'cached', pages that are searched.

There are two ways to view a cached page:

• Click the Cached link
  
• Use the cache: operator
  
  

Uses of cached pages

• To view the last versions of web pages not available anymore.
• To find out, when Google last indexed the page.
• To view pages with keywords highlighted.

Word stemming

When most appropriate, Google searches not only for your keywords, but also for word variations, such as plural form, cognate words, and so forth.

For instance, the following query

returns pages not only with 'instruction' but also with 'instructor', 'instructions', and many more.

If automatic stemming gets in the way, you can try phrase search with or without wildcard.