From Halopedia, the Halo wiki
Halo Fest was an event held by 343 Industries to celebrate the history of the Halo franchise. There have been two official Halo Fest events - one in 2011 and one in 2014 - alongside one held by GameStop in 2010 to celebrate the release of Halo: Reach.
Halo Fest 2011
Halo Fest 2014
Halo Fest 2014 was held in the Avalon Theater in Los Angeles on November 10, 2014 - one day prior to the release of Halo: The Master Chief Collection - and the event was livestreamed on Xbox LIVE and Twitch.