Unlike the post office, these racers go in rain, snow and mud (but as far as we can tell, not dark of night). Within these environments, there's a lot of stuff that can be run into and flung in different directions (unfortunately, this does not include spectators, but we can dream), but also some immovable objects like trees and rocks that'll slow you down and smash up your ride.
The heart of WRC is its Championship mode, which takes your driver and team through an entire series of races, keeping track of the points (or lack thereof) for the individual as well as his car manufacturer's team. As the configurable difficulty settings ramp up, damage to your car goes from aesthetic to impactful, so avoiding smash-ups becomes quite advisable. There are also some single races, quick races and a mediocre ad hoc wireless multiplayer option if you've got some equally equipped buddies in the general area.