The consuite is the central hospitality area at a convention, where all members are welcome to sit and relax, chat with other fans and help themselves to the provided refreshments. These usually include cold drinks and snacks, but may be more substantial.
This is a North American phenomenon; at most overseas cons, the bar provides a similar, if costlier, function. The size of the convention is inversely proportional, usually, to how central the consuite is to the social life of a particular con. At smaller events, everyone hangs out in the consuite; at larger ones, room parties are a more significant social venue. It's unknown when the consuite itself originated, but Don Ford referred to Room 101 as the consuite at Cinvention in 1949, according to Roy Lavender.
Contributors: Ditto 14 Progress Report 1, 2001, by Leah Zeldes Smith, loc by Roy Lavender, Ditto 14 Progress Report 2