I just hosted a soft opening at our union hall on Saturday, actually. A formal opening means everything is ready and you’re officially open for business. A soft open is usually unofficial, and stuff might not be completely ready. Our back room, for example, still needs carpeting, and there’s no sign over the door yet. A soft open is a sort of trial run which will tell you what still needs to be done which might not otherwise be obvious on the surface. Mistakes and rough edges are expected at a soft open.