Television
I don't think I have to explain to you what television is, but just in case; television is sometimes referred to as 'the idiot box' because it's a load of programs that just happen on the T.V screen, and whether or not you get to watch them is decided by if you catch it at the right moment because you do not control what is shown on each channel, you just choose the one you want to look at and sit back and enjoy the ride, idly sit by while this box that receives programs (television programs not like programming that typical old school nerds do, but more that the geeks of today do, with their love for film and whatnot, films are also broadcasted in T.V). I guess that's the basic idea of it.
ETV
ETV is T.V that you would get on a T.V but digitized so that you can get it on other things besides a T.V. - digital television broadcasting - ETV - think of it like sports and E-Sports, E-Sports are sports that you play on a gaming device, ETV is T.V on a computer.
Conditional Access
Conditional access is where they allow only people who have subscribed to watch what they are broadcasting, others are not shown the digital broadcast through such methods as scrambling and encryption, but that is only the unauthorized - that haven't paid for a subscription.
iTV
iTV is an example of ETV, on www.itv.com you can choose a program and just view it on your computer, a simple and easy to use, conditional access T.V on your computer. Oh yeah, did I mention it is conditional access, like it says above, you need to pay for to be able to use.