Stop words are words, which are partially or completely ignored by search engines.Words like, the, an, a, of, or, many, etc. Constitutes about 25% of the blog posts around the web. They have nothing to do with the content. Search engines, in both search queries and in results, often ignore them check out our list below.
There are many more just use common sense when using them. They have to be used but they are a way to set the content but not the contents.