EtherChannel: This is a link aggregation (port trunking) method used to provide fault-tolerance and high-speed links between switches, routers, and servers by grouping two to eight physical Ethernet links to create a logical Ethernet link with additional failover links. For additional information on Cisco EtherChannel, see the EtherChannel Introduction by Cisco.
LACP or IEEE 802.3ad: The Link Aggregation Control Protocol (LACP) is included in IEEE specification as a method to control the bundling of several physical ports together to form a single logical channel. LACP allows a network device to negotiate an automatic bundling of links by sending LACP packets to the peer (directly connected device that also implements LACP). For more information on LACP, see the Link Aggregation Control Protocol whitepaper by Cisco.
Note: LACP is only supported in vSphere 5.1, 5.5 and 6.0 using vSphere Distributed Switches (VDS) or the Cisco Nexus 1000v.
EtherChannel vs. 802.3ad: EtherChannel and IEEE 802.3ad standards are very similar and accomplish the same goal. There are a few differences between the two, other than EtherChannel is Cisco proprietary and 802.3ad is an open standard.
For more information on EtherChannel implementation, see the Understanding EtherChannel Load Balancing and Redundancy on Catalyst Switches article from Cisco.