Do you want to know about search engine or search engine optimization.If you are talking about search engine then type any search engine in your browser and type any words you want to search.Basically, a search engine is a software program that searches for sites based on the words that you designate as search terms. Search engines look through their own databases of information in order to find what it is that you are looking for.
there is a good guide for understand google, you should try search googleguide in google search engine