Performance Art is one of those areas of the art world that you either like or dislike. As for myself, the more zany and out of this world the more I am intrigued to watch. But I know for those uninitiated Performance Art can look like just a bunch of crazy people acting nuts. However, it is a medium of art that is so close to the human experience, that a painting or sculpture just can't radiate.
The Tate's glossery page describes the medium like this: