what is a spider?

depends in what sense a spider is an arachned (cant speel) that has legs 8 if i am right (okay i am tired).

But in the sense of the web a spider is a web crawler, in looks through websites following links throughout the entire internet.

As in the case of google the basics of page rank is a bot(spider/webc crawler) trapcing through all the web pages on the internet checking how many different places link to your website and depending on teh amount depends on your rank in the search engine.

From google:

Web spider
Software used by search engines to locate new Web pages for their document databases.

spiders are legal right?

yeah they are :)

how do you add the solved thing or whatever that we where asked to put?

nevermind I found it

Although its solved... just want to let you guys know that spiders are super easy to write... rather fun as well... makes for some good malicious code if you know what you are doing also ;)