Despite their differences, most approaches to studying language are based on the same common sense idea: language expresses ideas, meanings, messages, or bits of information that are developed and stored inside our brains or minds. For these theories, language is essentially a system of symbols that allows us to communicate our ideas to the brains or minds of other people. Such theories typically focus on what they perceive to be the key processes of communication.
The visual is quite helpful in understanding this concept.