Performances before the official opening, while the creative team is still making changes.
Previews are real, full performances in front of a paying audience that happen before a production officially opens. The director and writers watch how the audience reacts and keep adjusting: a song might be cut, a scene rewritten, a joke sharpened. Tickets are often cheaper, and you get to see a show before the critics do. The trade-off is that what you see may not be exactly what opens.
Also seen as: preview performance, preview performances, in previews