Yes conditionals were one of the first things to go into vb3 and that was before March 2002.
As for technical details:
1. You can do if/else constructs
2. The conditionals are parsed at the time you edit your templates since we now store two copies of every template. One with the conditionals asis, and one with any conditionals converted to accompanying php code so that there is no overhead when the templates are called by the forum.