Here are several downloadable file formats that contains all of the words and phrases Google and other search engines usually ignore, unless the stop word, contained within the search query, significantly alters the meaning of the search query.
Stop words is a phrase that really should be named 'unimportant words' because that is closer to what they really are but I guess SEO guys like to complicate things for their benefit.
Stop words are the words that really are not very important, at least in terms of searches on the the internet. They are words like a, it, why, they. In MOST cases these words are not important to Google, meaning, when Google scans your blog or website to interpret the content contained on your web pages, Google usually ignores these types of words and does not see them.
An example of a search query where a stop word is pretty critical to the search results, ie 'movie she is having a baby'. Someone performing a search on Google for this is obviously looking for information on a specific movie. If Google were to ignore the stop words in this query then the query would become 'movie having baby' which, obviously, would produce a much different page of search results.
