Time based art is when the artist has the control of a certain choreography of a sequence of images and/or live events and determines how the audience is encountering it. It usually also involves a number of media and is rather organized cross-media or inter-media.
While in traditional exhibitions of static objects the choreography how art objects are displayed is usually decided by a curator. This is not the case when it comes to artworks that are about choreography, such as film, video or performance related art works. We could argue that through time based work the artist is re-gaining the leadership and the decision of how the audience is confronted with the artwork.
This can also have the effect that the audience feels that the artwork is dominating too much. Like when confronted with long videos in museums it requires much time that I might not have planned before. Or when a performance is presented I just cannot watch a few minutes, go somewhere else and come back. I might not understand the work because I’ve missed the sequence of the individual acts.