Why are antennas satellite dishes?

Satellite dishes have the shape of a curve called a parabola, which is associated with the graph of second degree function.

We define parable from a straight line r and a point F, called focus, in a plan. The focus parable F and guideline r is the set of all points whose distance to the line r is equal to the distance to the point F.

Since the signals we receive from radios or light are very weak, when "caught" by the parable, it focuses them on a single point, the focus, which naturally magnifies them, and then reflects them.