This article is from the Satellite TV FAQ, by Gary Bourgois email@example.com with numerous contributions by others.
This is the most visible component, a parabolic reflector which may
consist of Solid Aluminum, Perforated Aluminum or WIRE MESH. Dish
sizes vary from small (3-4 feet KU BAND, EUROPE) all the way to
16-20 Ft (USA Commercial C-BAND) with the average falling between
7-12 ft, 10 ft being most common. This device focuses the microwave
signals coming from the satellites much as the mirror in a reflecting
telescope concentrates the light from distant galaxies.