An after-party is a gathering held after a main event, such as a concert, a premiere, an awards ceremony or a club night, usually for a more select crowd.
The word is older than it sounds: Merriam-Webster dates it to 1901, when it already meant a party for invited guests following a main event. Hollywood turned it into a competitive sport. For years the hottest Oscar-night invitation was the literary agent Swifty Lazar’s dinner at Spago in Beverly Hills, whose last edition was held in 1993; from 1994 the crown passed to a new dinner at Morton’s in Los Angeles, created by the Vanity Fair editor Graydon Carter with the producer Steve Tisch, which grew into the Vanity Fair Oscar party. In clubland the format is humbler but just as competitive, and the most coveted after-parties are never advertised, which feeds a thriving industry of people pretending to know where they are.