Difference between digital, HDTV and the normal TV ?

By 'normal' TV I assume you mean the TV that we have been watching for the last 50 years ? This is analogue. The transport medium by which the signal reaches you - say an RF carrier broadcast over the airways - is modulated with a direct analogue representation of the signal which emerges from the studio camera or other video source. The receiving TV set process this in an analogue form to produce the picture that you see (and the sound of course).

With digital TV, the transport medium is modulated with a digital representation of the signal from the camera. This digital signal is complex in that the source signal has been digitised, compressed, had error correction added and a couple of other clever techniques applied to help with the power / bandwidth distribution. It may also have had encryption added for pay TV access purposes. After it has had all of this done to it, it will be chopped up and inserted into a transport stream, along with sometimes many other channels. The TV set will process the received signal in digital format right up to just before the picture tube in a CRT set, or all the way in a plasma or LCD set.

High definition TV (HDTV) is just that. The number of pixels which form the picture, is higher than with 'standard' definition. Effectively, if you understand the concept of how a TV picture was formed on a CRT TV, it's like doubling the number of horizontal lines that the picture is formed from, and likewise, the number of individual points that can be resolved along each line.

Arfa

Difference in resolution and the delivery method, but all three provide the same boring garbage.