Time Division Multiplexing (TDM) is a technique that transmits multiple message signals over a single communication channel by dividing the time frame into time slots, with one time slot for each message signal. TDM transmits samples of each signal in sequential time slots using techniques like PAM. There are two main types of TDM: synchronous TDM where all signals use the same sampling rate, and asynchronous TDM where different signals can use different sampling rates. The document then provides examples and problems demonstrating the application of TDM techniques.