Question

What is the difference between a radius and an apothem?

Answer 1

An apothem of a regular polygon will always be a radius of the inscribed circle. It is also the minimum distance between any side of the polygon and its center.
good luck and hope that helps 

Answer 2

The radius is something you only find in circles or spheres .When you start at the center point and go to a point on the surface,the line segment you made is always the same length, the radius.

The apothem is used in polygons. This is because when you draw a line segment between the center of a polygon and a point on the edge, it can take on different lengths. the apothem though is always the one thats perpendicular to a side.