EtherChannel creates an aggregation that is seen as one logical link
You can have more than one Etherchannel between the same 2 switches
In this scenario normal STP operation will take over and block 1 EtherChannel port to prevent a loop
EtherChannel 1
EtherChannel 2
F0/1,/2,/3
F0/1,/2,/3
F0/21,/22,/23
F0/21,/22,/23