As opposed to an auditorium or hall, a black box theatre is essentially that - a black box.

The floor plan to such a space is usually a square, but sometimes is a rectangle. The walls, floor, and cieling are almost always painted black (duh). In such a space, the audience may sit on any, all, or some combination thereof of the four walls, usually in folding chairs or some manner of chair that can be removed from or about the space. Some spaces feature a removable wall, so that one side of the theatre may open into an adjacent space, providing additional seating for patrons.

Some theatres may feature an upper level, usually nothing more than a catwalk along one or more walls of the theatre. There may be space to hang lights on the walls or in the corner, but they are usually suspended in the "flyspace," even though there is little to none of this in the typical black box. The stage manager(-s: though no production done in this space will be very large, usually only one is required) may sit in a small booth adjacent to the space, with a window looking into it, though many calls can be made with no better idea of what's going on onstage than what comes through the house mics.

What is the point of using such a space, you may ask. The two main reasons are flexibility and intimacy. Firstly, since the space usually has so few permanent fixtures, a lot can be changed and tailored to fit each particular production. Since there is usually no actual set built into the theatre (just the floor), an individual piece can be built to suit the specific needs of the play; incorporating a rake or not, allowing the actors to play to all four sides or not, etc. Secondly, in a black box, the audience is seated much closer to the stage and actors. This configuration is especially effective for one-man shows and other narrative works. Also, the director may choose to present a work in theatre in the round, which a black box is optimal for. The biggest downside to this is that productions of this style are notoriously hard to direct, stage, and act, because the actors’ backs are always to a quarter of the audience.

In any case, the black box theatre is very well suited to certain types of theatre productions, however it usually takes a talented director and cast to make it work effectively - but when it does, it makes for a theatre experience unlike anything you'd see in an auditorium.