This is going to sound incredibly naive but I haven't played any turn-based games. I was always playing actual AD&D until Baldur's Gate came out (yes, I WAS living under a rock). Would someone be kind enough to explain it for me?

Hopefully this will help.

Turn-based combat goes in a sequential order that is determined by character initiative. The easiest way to explain initiative is that if you have the best roll your character gets first swing. Here's an example. Your party consists of one barbarian and one sorcerer and they encounter 3 skeletons. The DM (your PC) rolls for initiative and your barbarian rolls highest, followed by skeleton A, then your sorcerer, followed by the remaining two skeletons (B & C). The barbarian gets first swing at skeleton A. That is the end of your barbarian's turn. Skeleton A was next so it takes a stab at your barbarian. Turn completed. Sorcerer casts a spell that takes three turns to complete. This makes it skeleton B's turn, then skeleton C's turn. After those two turns are completed, it's back to your barbarian. He makes a fatal blow to skeleton A, which ends that turn but because this makes three turns completed, your sorcerer's spell gets launched desecrating the two remaining skeletons.

Actually that did help. Thanks! I know about initiative but I wasn't sure how it ran on a computer game but it's clear to me now! :)