EtherChannel is a way to bond multiple same speed links together and have them act as one link. One huge benefit of this is to reduce convergence in a STP environment. The reason this eliminates convergences is due to the face that if one bonded cable fails STP will not recalculate since another cable is still active and able to receive data.
SW1(config-if)#channel-group 1 mode on
~enter this command on up to eight interfaces that will join an ether channel, this command creates group one for other ports to join.
Verify it worked - notice it says channel-group 1 mode on in the running config