A digital communication systems offers many advantages to the user, that cannot be achieved with a analog system. Digital communication system may make use of analog links and concepts.
A digital system is a more general case of a binary system. In binary systems, only two signals values can exists. They are often called 0 and 1, but these names represent specific voltages.
The term data is commonly used in digital communication systems. Data is any form of information, that has been put into digital form, so that it can be handled by a digital system. The data itself is measured as bit.(bit is a contraction of the term 'binary digit')
The binary signals are easy to generate and process with digital circuits. These digital circuits are available in the IC form and can generate and process digital data at high speeds.