how do people communicate?describe the process?

Answer 1

... You do realize that you just communicated your question to everyone willing to read your question, right? And that by communicating, you had to go through the process of communication, thus you could just think back to what you did in order to get your answer.

Or perhaps you mean something a little more specific than a basic, fundamental action that by expressing you non-understanding you provide the very means with which you might understand?

Answer 2

In a simple, form, we have two people.
The expressing end comes up with an idea, retrieves the words (or signs) to convert the idea to language, and then expresses it.
The receiver then takes in the information via auditory or visual systems. Auditorily, the information passes through the auditory system, changing from acoustic to mechanical to hydraulic to chemical-electric in the central auditory pathways to the auditory cortex in the temporal lobes, where it is processed and understood. Visually, the information passes through the eyes and into the brain via the optic nerve into the occipital lobe where it is processed and understood.
The receiver then becomes the expresser, and the expresser the receiver, and the story continues.

Every conversation starts with an initial greeting, could be eye contact, or tapping on the shoulder, or simply saying hello. It then takes a turn-taking process until the conversation has exhausted, at which time the participants end the interaction.