Hi electronics_kumar,
purpose of the source coding is to eliminate redundant data from a signal. For example, if your digital data contains many '0' as in the sequence "000010100010000011", then it is much more efficient to code that long data into "52461". "5" means that there are 4 '0' and one '1', "2" means there is one '0' and one '1', etc. In reality, indeed many physical signal such speech and image contain many redundancies, so source coding is very important. By using source coding, people could design many data compression algorithms to save data efficiently, or reduce the bandwidth for transmitting communication signal via a channel.
The purpose of channel coding is to introduce redundancies into information data. This seeems like a contradiction with that of source coding. But you must be aware that channel coding introduces redundancies in a controlled manner, whereas redundancies inherent in physical signals are random (uncontrolled). This redundancies introduced by channel coding are very important to reduce (or in some cases eliminated) the errors which may occur when you transmit or save/record information data.
best