Today, nearly all electronic devices we use are digital. The main
reason for the change from analog to digital is because digital signals
are easier to transmit and are also more reliable.
A digital system is one that uses discrete values (often electrical
voltages), representing numbers or non-numeric symbols such as letters
or icons, for input, processing, transmission, storage, or display,
rather than a continuous range of values (ie, as in an analog system).
The distinction between "digital" and "analog" can refer to method of input, data storage and transfer, or the internal working of a device. The word comes from the same source as the word digit and digitus: the Latin word for finger (counting on the fingers) as these are used for discrete counting.
One key difference between analog and digital transmission involves the bandwidth, or transmission capacity required for both schemes. Analog signals require much less bandwidth, only about 4.5 MHz with a 143.2 Mb/s data rate. for the average NTSC video signal. By comparison, some digital video transmission standards require as much as 74.25 MHz with a data rate of 1485 Mb/s. Advances in single-mode optical fiber make these higher rates more accessible for longer distances. Copper coax fails to perform at these data rates.
Another difference between analog and digital transmission deals with the hardware’s ability to recover the transmitted signal. Analog modulation, which is continuously variable by nature, can often require adjustment at the receiver end in order to reconstruct the transmitted signal. Digital transmission, however, because it uses only 1’s and 0’s to encode the signal, offers a simpler means of reconstructing the signal. Both types of modulation can incorporate error detecting and error correcting information to the transmitted signal. However, the latest trend in signal transmission is forward error correcting (FEC). This scheme, which uses binary numbers, is suited to digital transmission. Extra bits of information are incorporated into the digital signal, allowing any transmission errors to be corrected at the receive end.
So Digital Transmission Systems are better because they eliminate the effect of noise completely. You don’t look and listen to a received signal from an original recording, but you look and listen to a reproduced signal of the recording. The reproduction comes from an exact copy of the original recording.
The quality of what you see and hear now depends on your TV and Sound System. A high quality TV and Sounds System will give you high quality Video and Audio. The negative effects of the (still analog) transmission have been eliminated from the process.
Satellite TV makes use of Digital Transmission Systems. What you see at home will always be of Digital no (much less) noise Quality.