Crits are small loops (less than a mile) with four or more cornors, and most are fairly flat. They are generally shorter events compared to road races. In Crits bike handling skills and sprinting ability are the two most important things. Road races are larger loops (bigger than a mile, but normally a bit bigger). Also road races are generally hilly and longer events (severial hours). In a road race climbing and time trialing (to create a break) are the two most important skills, although you still need to be able to sprint to win. Hope this helps.
-Matt-