Carrier Sense Multiple Access (CSMA) is a network protocol used to manage how devices share a communication channel. It requires each device to listen to the channel before transmitting data. If the channel is clear, the device can send its message; if it detects another transmission, it waits until the channel is free. CSMA helps reduce data collisions, which occur when multiple devices transmit simultaneously. This method is commonly used in Ethernet networks and wireless communications, ensuring efficient use of the channel and improving overall network performance.