Way too ambiguous of a question for an intelligent answer.
Saying "the 3 parts to communication" implies an assumption that there ARE only 3 parts to communication. So you are probably asking based on learning of or being taught an approach to communication that uses 3 parts.
MY ANSWER: Ask the question in a better way, with no assumed truths. Example: "What are the basics of communication?" "How can I become an expert at communication and/or persuasion?"
FACT: The superior way of finding answers and achieving results in ALL of life is to FIRST ask the right question.
Proof: "You send a message...someone receives that message...they process that message....they respond to that message with a message..." That is four parts. I could list communication methodologies that have many more parts. It depends on your use of knowing.