Bar Citizen is the general term for any meetup of Star Citizens, run by the fans, for fans.
Those meetups vary from a small size anonymous meeting at a bar to overtaking a gaming bar for a night with live streaming, free drinks, prizes such as ship models, writing your name in an alien language etc.
Hundreds of individual Bar Citizen events have taken place throughout the world.
Cloud Imperium Games developers may attend those events, with various goodies and loot in tow (including Banu cubes).[1]