Search engines are divided into two main types: those that use a keyword search approach and those that categorise the Web into a series of hierarchical topics.
To use the keyword engines, you type a single word or phrase and the search engine returns a summary of pages or resources which contain a match. You then browse through the results list, select a likely looking document and activate its link to view the page.
To use the category searches, you start with a general topic, such as Arts, Business, Computers and so forth, and then on to specific category, such as Poets, Credit Cards, Software... refining your search as you go.
The major search engines work in a similar way, at least at the elementary level, however to use search engines effectively you will need to know the specific syntax they use. Each uses its own search language, and the syntax varies slightly from one search engine to another. Many search engines allow for the use of Boolean Logic in the search expression to further refine your search.
Meta-search engines employ a different approach. These search engines take your search query and submit it to a selection of other search engines, including both keyword and category engines. Meta-searches usually restrict the number of results either by limiting the amount of time they spend on the search, or by limiting the number of documents in the results list.
For many searching the web is synonymous with Google. There are however quite a few search engines and searchable indexes.