What helps you in finding a book in the library?  The answer is – Index.  Similarly Google indexes your site so that you come up in search results.   Googlebot crawls your site and gives a unique ID to each page it has found. It lists every document that contains a certain word.  For example, for my site Googlebot would list ‘Web Design’ or ‘Web Designers’ for certain pages.  Stop words are words that Google does not index.  A few of these words are , a, about, an, and, are, as, at, be, by, for, from, how, in, is, it, of, on, or,
that, the, this, to, was, what, when, where, who, will, with.