My Lion King Forum

I've seen websites like Google browsing the forum with their accounts. They seem to be labeled "bot" sometimes, and "spider" other times. What's the difference between the two, if any?

There isn't much of a difference. Spiders download webpages and bots peruse them and execute a predefined function such as index the page for use in a search engine.

What do spiders do with downloaded webpages? o.o

It can vary...a good example is the web archive spider that downloads webpages to archive them: http://www.archive.org/web/web.php

Ok. And finally, crawlers?

I think crawlers are just a name for bots and spiders that "crawl" the web by following links on the web page itself.

They are definitely loose terms, and some programmers define them differently than others. Their meaning is somewhat lost and people use them interchangeably. Personally, I call everything a bot. :]