Channel bonding is a practice commonly used in IEEE 802.11 implementations in which two adjacent channels within a given frequency band are combined to increase throughput between two or more wireless devices.
Channel bonding is also known as Ethernet bonding, but it is used heavily in Wi-Fi implementations. It has become a very popular technique in the world of Wi-Fi because its increased throughput provides for more functionality within Wi-Fi deployments.
Techopedia explains Channel Bonding
Channel bonding is commonly practiced in Wi-Fi networks, which typically operate within the 2.4 GHz frequency band. The 2.4 GHz frequency band has room for three non-overlapping bonded channels. Within 802.11n deployments this translates into a theoretical throughput of 54 Mbps. The combination of these non-overlapping channels is often referred to as increasing the size of the pipe.