What is MUX bitrate?

Can you please explain what MUX bitrate is in simple terms? I've heard the term before but I'm not entirely sure how it relates to the transmission of data, particularly in the context of multimedia or streaming services. Is it related to the speed at which information is sent or received? And how does it impact the quality of the content being transmitted? I'd appreciate it if you could provide a clear and concise explanation of this concept.