Analogue vs digital signals
Analogue signals contain all the information as a continuously varying wave - such as on an oscilloscope screen when you speak into a microphone connected to it.
For example the sound from an orchestra will consist of many different instruments playing many different notes at the same time. The human ear can distinguish all this and make sense of it even though the sound wave received by the microphone will simply be a complete combination of all these sounds. It is this combination of sounds that is transmitted to your radio or television as an analogue wave.
Digital signals are a series of pulses - ons and offs, or 1s and 0s. The sound of an orchestra has to be encoded to digital form before it can be transmitted and has to be decoded back to the analogue sound wave before the listener can make sense of it.
The advantage of digital signals is that they are much less likely to be degraded by interference (noise). It's also possible to send a lot more information digitally (e.g. more television channels) than using analogue technology.
The other advantage of digital signals is that they can be sent directly to computers which, after all, use digital systems themselves.
The signals from a satellite are digital. They use a system called 'packet switching' which is the same as used in computer networks and for the internet. This system is particularly effective for dealing with noise.