The Internet Group Multicast Protocol (IGMP) is a communications protocol used by hosts and adjacent routers on IP networks to establish multicast group memberships. The host joins a multicast-group by sending a join request message towards the network router, and responds to queries sent from the network router by dispatching a join report.
General notes:
switch(config)# interface vlan 1
switch(config-if-vlan)# igmp
show ip igmp-snooping vlan 1 should show IGMP enabled on the VLAN, but no IGMP Querier set.