Pip, Thats not a dumb question, I hope I don't give a dumb answer, but here it goes! The link Hoser put up nails it. A search spider or web crawler is a program that search engines, (like Yahoo or Google), use to gather information on the internet. They are out there all the time, you just don't know it.
Before I posted this, I looked on the "Who's Online" link. There were 36 Registered Users and 170 Guests on Brown Cafe. Out of these Guests, Yahoo had 31, MSN had 5, and Google had two. If you look on the Map with all the red dots, I find it interesting that no matter what time of the day, there are about four of these bots online in China monitoring this site. They use a different name, I no longer have access to that feature that names them.
Its just the way that the internet works. Normally this site has 2500-3000 people log on it everyday. The "Slurp Spiders" are just gathering info so the rest of the web can find it. We have a lot of Users on this site with more technical expertise, maybe one of them can chime in with a better explanation.
Hey Scratch.... Dumb question alert! 
Sounds like something Larry the cable guy might say. 
