Communication is simply the act of transferring information from one place, person or group to another. Every communication involves (at least) one sender, a message and a recipient. This may sound simple, but communication is actually a very complex service. The transmission of the message from sender to recipient can be affected by a huge range of things. These include emotions, the cultural situation, the medium used to communicate, and even location. The complexity is why good communication skills are considered so desirable by employers around the world: accurate, effective and unambiguous communication is actually extremely hard.
The sender ‘encodes’ the message, usually in a mixture of words and non-verbal communication. It is transmitted in some way (for example, in speech or writing), and the recipient ‘decodes’ it. Of course, there may be more than one recipient, and the complexity of communication means that each one may receive a slightly different message. Two people may read very different things into the choice of words and/or body language. It is also possible that neither of them will have quite the same understanding as the sender.
In face-to-face communication, the roles of the sender and recipient are not distinct. The two roles will pass back and forwards between two people talking. Both parties communicate with each other, even if in very subtle ways such as through eye-contact (or lack of) and general body language. In written communication, however, the sender and recipient are more distinct.