Quote - What is a BVH file?

It stands for (B)io(V)ision (H)ierarchy file... it's a data file that contains information about the relative motion of bones in a 3D model. They're often made by capturing the motion of live actors. You can do some impressive animations with them, but they can be tricky to use. If the bones are misnamed, or the scaling is wrong, or the motion in the file goes outside of the constraints of the character, your ballet dancer can end up doing an impressive imitation of an epileptic fit.