HD?

DISH is confusing me somewhat.....there are two dishes on the roof, and one says "HD", and it aims south and so isn't blocked by the trees that have been messing with some of the channels I like.....and now all of a sudden ALL of the channels I usually watch are seemingly in HD, so I don't get interference anymore because they are all being fed to the clear dish? I think that's what is going on.....almost everything I watch has the little HD sign when they show the channel logo.....fine with me.....