This search may have limitations on its depth and domain access, but it is simple straightforward algorithmic method that is used in most search engines. The next part of the search is sorting out these pages when you submit a query to the engine. It usually uses straight keyword matching to the pages. If enough matches are made between the Boolean expression you submit and the text of the page the URL is returned to you as a search result. This of course, does not always work very well.
Most crawlers use strictly text based search techniques.
To help this, many pages include META tags, which provide textual information on inserted multimedia. This is one way authors solve this problem, but the search engines have no way of explicitly extracting this information. One thing that many web pages use to search text is stemming. They take a word you submitted and add on language prefixes and suffixes and then search for similar results. Most web searches are also more sensitive to the context at the top of a web page than anywhere else.