I've been to tons of them. It's where someone organizes that a bunch of people will go away for a weekend and sew/quilt all weekend long. Usually someone else does the cooking so quilters can sew. Usually there is a common room where everyone puts their sewing machines and "stuff". That common room needs to have a lock on it, and the last person to bed locks the room, giving the key to the front desk. The first person up in the morning opens the room. Because our equipment/tools/fabrics, etc can be quite expensive, there always has to be someone in the room at all times (this is especially true if it's in a hotel where other guests are staying).
Some are very structured with classes at set times, others don't have any classes at all.