Why do search engines often show a too large number of total results? [closed]

"Search engines like Google do not really evaluate the query. What they do is evaluate the first part of the query, meaning enough results to display the first result page.

That's because Google works under time constraints, needing to give a result in a matter of seconds, while for some keywords there are result sets pointing to millions (or more) of indexed pages.

The total count Google gives for the result is only a statistical estimate. It's evaluated as a function of the number of results that were found, and the fraction that the displayed result represents of the total size of the indexes that are to be processed per all the keywords. In other words, if giving you the first 20 results involved processing 20% of the index sets, then Google will stop processing and return an estimate for a total result size of 100.

When you click on a result, you might not find your keyword inside. That's because while Google reindexes all pages, it does take a long time to recrawl over billions of Web pages. So if the page has changed, Google may be late by several months to take notice of the change."