A message in its most general meaning is an object of communication. It is a vessel which provides information. Yet, it can also be this information. Therefore, its meaning is dependent upon the context in which it is used; the term may apply to both the information and its form. The goal of a message is to pass information between communicators (human or non-human).
There are two main senses of the word "message" in computer science: messages passed within software, which may or may not be human-readable, and human-readable messages delivered via computer software for person-to-person communication.
Questions having the messages tag regards the User Experience of messages.