What is the definition encoding and decoding?

Encoding is writing a large piece of data using codes. These codes are like hiding the actual message in encrypted form.

Decoding is getting back original message from the encrypted message

then what is redundancy. can u explain what exactly means codes.

It is process of representing larger data using smaller encrypted data Codes or short hand version of the actual message

S.PRAGASY

then what is redundancy. can u explain what exactly means codes.

Consider this example for understanding :
Suppose we want to encode the message: Hello
We move each alphabet to the next alphabet in the English language, (i.e A becomes B and B becomes C etc).
The code we get is :Ifmmp
This process is encoding , we can decode this by following reverse procedure in this case , thus Ifmmp---> Hello, (this is decoding)
This is the basic idea. Hope it clears your doubt.😀 .

Encoding, which is most of the times confused with Encryption (as even done a post above me), is the technique to represent a data into some another form than its original. This is done more with an intention of compressing or to have better control over the data, as opposed to the thought of hiding it. To illustrate, lets take an eg., a seven segment display, you'll need 7 control signals to operate it. That means, 7 single bits for each of the segments. Now assume you've this 7 segment display kept apart and you're remotely sending signals to control it. We know that 7(decimal)can be easily represented using 3 bits, so while transmitting, you'll only send 3 bits which could be later converted into 7 single bits required by SSD using a decoder. Hence, you've gained a speed in transmission since you sent only 3 bits instead of 7 bits otherwise. The penalty is increase in hardware, but you gained performance. This is just a very basic example and encoding could be very complex and sophisticated as well.

Now a days, the encoding scheme involves various error checking as well as correcting mechanisms which allows you to detect as well as correct the errors at the receiver. This couldn't have been possible if you would've sent raw data directly.

[Prototype]

Encoding, which is most of the times confused with Encryption (as even done a post above me), is the technique to represent a data into some another form than its original.

Well the definition of Encryption is same:

Technique to represent a data in some other form than its original

, but as u correctly stated difference lies in purpose,
but in the post above yours I no where mentioned its purpose as "thought of hiding it"
The example that both of us gave served same purpose : To convert data from one form to another, it is just that my example was similar to examples taken in books while explaining encryption, which might have led you to assume that I was talking about encryption.