Bundling multiple ports into one logical interface is a common configuration. It is otherwise known as bundling, port channel or EtherChannel. You can combine multiple interfaces into one of these three modes:

- LACP

- PAgP

- On

LACP

Link Aggregation Control Protocol is the standard 802.3ad. You combine multiple links into a single logical link to increase bandwidth and redundancy. All links participating in a single logical link must have the same settings such as duplex mode, link speed, and interface mode such as access or trunk. You can have up to 16 ports in an LACP EtherChannel but only eight can be active at one time.

LACP can be configured in either passive or active mode. In active mode, the port actively tries to bring up LACP. In passive mode, it does not initiate the negotiation of LACP.

There are a few parameters which can be configured with LACP ports:

- System Priority - Forms the system ID and is used during negotiation.

- Port Priority - Used to decide which ports should be put in standby mode when there is a limitation or something preventing a port from aggregating.

- Administrative Key - Defines the ability of a port to aggregate with other ports.

In the event one of the links within an LACP bundle fails, traffic continues to flow on the other available links in the bundle.

PAgP

Cisco's proprietary alternative to LACP, Port Aggregation Protocol. It also creates Etherchannel links and is configured similarly to LACP. Configuring PAgP properly and it will automatically configure individual ports into a single logical link.

There are two modes for PAgP:

- auto - This is the passive negotiating state which responds to PAgP packets.

- desirable - Places interface into an active negotiating state.

Having two ends of a PAgP link in auto mode will not result in a PAgP link because neither will negotiate to bring up the PAgP EtherChannel. PAgP protocol data units (PDUs) are sent and received on the lowest numbered VLAN of the trunk link.

You can have up to eight ports in a single PAgP EtherChannel. Just like LACP, all ports in a PAgP EtherChannel must have the same speed and duplex settings.

EtherChannel Manual

Switchports can be configured to bypass LACP or PAgP by simply changing the mode to on. This mode is used to manually configure EtherChannel. This mode can be used if the device on the other end doesn't support PAgP or LACP.
https://mobileinfoworld.com/configuring-lacp-pagp-manual/