I believe its like extra programs you can install within the vboard, that doesnt already come with it. Sometimes you dont know if it will work properly so you have to be a pretty good "hacker" to make it work.
Correct me if I'm wrong Anne... I've never actually done it but the webmaster of my board has for many features.
Yep - that's pretty much it It's a PHP script that's meant to be incorporated within the Vbulletin forums software. It's totally legal and the VB site sends you to the places where you can find the hacks (there are hundreds if not thousands of them), but they are not officially supported by VB so if you have a problem you won't get tech support for a hack. As I know very little PHP I try to steer clear of hacks and stick to the official software.