David is basically right, except trainers with dihedral and flat bottom wings will often turn with only aileron input. It will turn at a faster rate by adding elevator and aileron. While you are in the early stages of learnig to fly only use the rudder while the plane is on the ground. Once you are airborn at a safe level then you can turn using ailerons and elevator if neccesary. It takes some practice to do coordianted turns.

Have fun!!!