Multiplexing is a technique used in communication systems to combine multiple signals into one signal over a shared medium. This allows for more efficient use of resources, as several data streams can be transmitted simultaneously without interference. Common applications of multiplexing include telephone networks and data transmission over the internet. There are several types of multiplexing, including Time Division Multiplexing (TDM) and Frequency Division Multiplexing (FDM). TDM allocates different time slots for each signal, while FDM assigns different frequency bands. Both methods help optimize bandwidth and improve the overall performance of communication systems.