Multiplexing is the method of dividing a physical channel into many logical channels so that the independent signals may be simultaneously transmitted to network.
It is also known as muxing.

Categories of Multiplexing
1. Analog Multiplexing:
FDM (Frequency Division Multiplexing)
WDM (Wave length Division Multiplexing)

2. Digital Multiplexing:
TDM ( Time Division Multiplexing)