Okay, admit it. You do email, you can look things up on the web, maybe you can even find the tilde key. But you don't really know some basic things about computers--like what a search engine actually does.

Feel no shame. We at Moment of Science are prepared to help. A search engine is just a system set up somewhere that does the hunting for you. You type in "Jennifer Lopez" and the search engine gives you a list of ten thousand sites where the feisty Latina singer is mentioned. How did it do that?

First, here's what it didn't do. It didn't receive your query, turn its attention to the entire web, and start looking for places where the letter string "L-o-p-e-z" is found. Try that and by the time you got an answer she would have been married three more times.

Instead, it uses what's known as "preprocessed data." That means it has a Jennifer Lopez index file already generated, and is using a program called a "crawler" to keep checking the web for more hits. In a sense, it's always searching the web before you want to, one step at a time.

Notice, though, that what a crawler looks for is just the words "Jennifer Lopez." If you make a web page advertising chili that's "hotter than Jennifer Lopez," boom, up it goes into the index file. That's one reason search engines still give us uselessly huge numbers of hits. Many use what are called "ranking programs" to try to cut down responses, but looking for Jenny without getting Craig or Jones is still a challenge for computers of tomorrow.