C-Band TV refers to the large (6 to 12 foot in diameter) satellite dishes that you have seen in backyards for the last 15 years. Contrary to popular belief, the large dishes are not dinosaurs; they are not antiquated; and they are not becoming obsolete. Sure, the little dishes are cute, but they are no substitute for the big dish. In the case of Satellite TV, bigger really is better. Millions of dollars in advertising by the little dish companies will try to convince you otherwise. They talk of "digital quality", but digital doesn't necessarily mean better. Have you ever seen an AVI played at full screen? That's digital, but is it better? Bottom line, see for yourself.

Here is a good link to explain the benefits of C-Band TV.

4DTV is a receiver (set-top box) for your C-Band TV satellite system. As mentioned above, the little dish advertising and sales people will try to tell you that the big dish is obsolete, and you should get a little dish because it is digital, and digital is the wave of the future. Well, the 4DTV receiver can receive both analog and digital signals, so it is also a part of that digital future. Don't be fooled by the hype. By combining both analog and digital in one box, the 4DTV gives you access to over 600 channels today. This is possible because the big dish is movable, unlike the little dishes, which are fixed on a single satellite position. The fixed satellite position means limited capacity, and more compression, which impacts the "digital quality" dream.

Here is a good link to provide more details about 4DTV.