Quick Definition: An official host of an event, party, or performance responsible for keeping the event flowing smoothly and entertaining the audience during session transitions and breaks.
“MC” is an abbreviation for “Master of Ceremonies.” Depending on the event, the MC usually presents performers and also speaks to the audience and keeps it “moving” during event transitions.
The MC is usually not the actual performer, although he may perform during certain transitions to entertain the audience. This role is important, and, if the MC is bad at hosting, the whole event will be at risk. Similarly, a great MC can make the different between a bad event and a great event. When hosting fashion shows or event based parties, make sure you have a great MC to coordinate the festivities. This will ensure the highest praise for your events and build social proof.
Russell Brand doing a promo for hosting the VMAs in 2009: