Yes, these are digital video cameras. They write onto miniDV cartridges. You use firewire to move the data to a computer and edit it. The GS120 is an old model - it's been replaced by the GS150, which has more pixels. The GS250 looks similar to the 150, but is higher resolution. Here's a side-by-side review of the two. You may also want to look at the GS400, the comp Sony models, and the Canon Optura models. I don't know much about the other brands, but the VX2100 that Ptravel recommmended looks really nice. It's almost certainly a better camera than the GS150 or 250. I'd guess it's more comparable to the GS400.

The GS120 communicates flawlessly with my iBook. I plug the firewire cable in, and that's about it. No drivers to install or anything. One of the best things about the Mac is the seemlessness of the experience with my cameras - both still and video. The iBook is okay for video editing, but if I were going to spend most of my time doing it, I'd want something faster.

I feel like every time I post I add to your confusion. Sorry. I always have a hard time making purchasing decisions like this, too. I agonized over the camera choice for weeks. You ought to go to a store and play with them a little. If you can, buy it somewhere without a restock fee. If you're unhappy with it, take it back.