The Cumulative Normal Distribution

The integral of the Normal Curve is the Cumulative Normal Distribution.  Unlike the Normal Curve, which stretches from negative infinity to infinity, the Cumulative Normal is bounded by 0 and 1.  This unique distribution gives the relative frequency with which observations are expected to be smaller than (or to the left of) any given value on the Normal Curve.

The Cumulative Normal Dist.: An Animation

Distributions come in shapes other than the standard bell curve.  There are other distribution types you should be made aware of.