Ok, Antennas come in 2x2 types
Roof top (usually automatic) and Portable
Dish and dome
Domes can see ONE satallite at a time, And only one Frequency band. Work well with a SINGLE CHANNEL DISH receiver.. Do not work with DirecHDTV (work for the time with SDTV but that is on the chopping block in a few years).
NOTE: if you have more than one receiver, or a multi-channel receiver, Domes only work when all receivers want the same satallite, both services use 3. And again Domes on Direct only work with one of those. The SD one.
DISH type antennas: there are several types.. You get the one that matches your receiver and service, be it Dish or Direct, and it WORKS.. Well, Usually.
Rooftop or Portable.
A fully automated Rooftop, You park, push button Watch TV.. BUT... What if you are parked under the evil signal eating tree? (No joy there)
Portables set up takes a bit longer, epically with a DISH, but.. You can set it up away from said tree.