An involute is the shape formed by a curve that is perpendicular to a line that at every point is tangent to the base circle. That's a pretty confusing thing, the easiest way to explain it is that it's the shape made if you do the following:
Wrap a string around a cylinder that has the diameter of the "base circle" (a circle which is roughly the root of the teeth). Now tie a knot in the string, and keeping the string taut, unwind it from the cylinder. The path taken by the knot is an involute. The involute shape is modified to contain a radius at the root of the tooth for strength, and it is chopped off at the tip (it would otherwise form a sharp point).
Is that enough to get your job done?