The two most common tools are the Internet search engine and the Internet guide. Understanding how each works is the key to finding what you need on the web. An Internet search engine collects information fairly indiscriminately through the use of programs known as crawlers, spiders, or robots.
Crawlers fan out across the Internet and collect copies of web pages from various host servers.
These files are then assembled into a database. When a query is posed by the researcher, the search engine looks for likely matches within this database. The search results are then displayed and ordered according to relevancy. Different methods of relevancy ranking, in part, explain why different search engines return different results for the same search query. Each search engine is uses slightly different language.