Dumb processor question and memory question

How do I find out the speed of my processor? I've got an iMac from around 1999. I think it's the first one. It has a pull out CD-ROM drive.

Also, kinda unrelated. Where can I learn about memory and reallocating it. Also what defragmenting (is that what it's called?) is. I know how to see stuff at the About This Computer, and that when you open an application it tells you how much memory it takes up. But I don't even understand how much I have. Then, what virtual RAM etc. etc. I've got a lot of basic questions and don't want to keep bothering you guys.

If you can point me in the right direction toward info. I would truly appreciate it.

Thanks so much.