Without going overboard on tech speak - passive and active is for impedance matching between the guitar and the mixer (or computer card). If you have active pickups its not an issue, but if you put a passive guitar straight into a desk the sound will be somewhat dulled.
if you want to take a clean sound into the computer and do the sound processing there, you just need a basic DI box. If you want to have a distorted sound going in, then you need something with a speaker simulator - personally Ive recorded with a Palmer, an Award pre-amp, and now a demonizer for getting the amp sound to tape, all worked fine for me, just needed a few different tweaks.
Cheers