Bening case: The screw holding the agitator fell off. Find it and put back in place.
Intermediate case: The coupling between the motor and the transmission is detached or broken.
If detached, fix it back in place.
If broken, it may be easy to very difficult to repair. It depend on exactly what is broken and how it's broken. It could be only a belt to replace.
Mine use a kind or leather tube with 4 slits along it lenght, held in place at both ends by a collar. If your's is similar, you can make a new one yourself...
Terminal case: The transmission is broken. Getting a new one can be next to impossible, especialy if it's an older model. It may cost less to get a new washing machine that to repair it.
Electro
February 2013