The difference between a convection oven and a regular oven is that a convection oven has a built-in fan. The fan continuously blows hot air on and around food. With hot air blowing and moving around the oven, food tends to cook much quicker. The rule of thumb for cooking with a convection oven is to decrease the temperature about 25 degrees from what a recipe calls for. The way to best learn is to just start using it and to monitor the results and then adjust temperatures and time accordingly.
Convection Oven 101
The Martha Stewart Show, January January Winter 2007 2007