This screencast is all about polar coordinates. They are merely another way of locating points in a plane. Rectangular coordinates are limited to moving horizontally and vertically from the origin until you reach your point’s location. With polar coordinates, you stand at the pole (the origin), rotate through an angle until you are facing in the right direction, and walk out the specified number of units (the radius).
Why do we need another way of plotting points? Well, rectangular coordinates are very handy, but sometimes a relation’s or function’s equation is far simpler when written in polar form. Take circles: in rectangular form, a circle centered at the origin with a radius of 3 has the equation x^2 + y^2 = 9. The same circle in polar form is r = 3!