[nathanww]

A "periodic" function is one that is run only at a certain interal--if you look in the c++ reference, you'll see there's actually a function to set how often it runs.

A "continuous" function is called as fast as the robot is able to--there's no way to explicity specify when it should be called.

As for how they interact---the system considers them two functions of the same class. This means they can both use global variables in your file, call each other, etc.