Hi ajkelsey,
A line can consist of more than 2 points, or vertices. When using the line tool a single click of the left mouse button places a point of the line. Double clicking the mouse completes the line.
Since a circle can be defined by its center (first click) and a radius (mouse drag) completion can be indicated by depressing the mouse button.
The Freehand line tool provides an experience similar to drawing a circle. The drag of the mouse inserts the needed vertices of the line. Depressing the mouse button completes the line. Since the line is being drawn "freehand" style it most likely will not be straight.
For more information please see the help topic Work with graphic elements in a map.
Hope this helps,
Tom