What is the meaning of encoding and decoding a message?

It looks like that the question is about the the steps of coding and decoding in the process of communication. The entire process starts with the sender of the communication having a thoughts in mind which needs to be communicated. This thought than is coded - that is converted in a form which can be sent or transmitted from sender of communication to the receiver, The process of coding typically involves representing the thoughts of information to be communicated in some form of language. This is first done mentally then represented in some physical form like written or spoken word or some other forms method physically representing and transmitting data. The coded data is then transmitted or sent to the receiver of the communication.

The message transmitted thus teaches the recipient in the form of some physical representation of data. This physical form of message is perceived by the recipient through sensory organs. Typically this involves some activity like hearing, reading, or seeing. Whatever is perceived by the receiver of the message is then mentally decoded back in the form of thoughts in the mind of the receiver.The thoughts created in the process of decoding makes up the understanding of the message by the receiver.