Why want my washer drain the water?

Why want my washer drain the water?
I had a friends washer not drain. In her case there was a sock stuck in the pump that pumps out the water. The pump was in a translucent plastic case, I could see the sock move around in the pump when I rotated it by hand. Turn off the power, take a cover off, look at the pump. There could be a broken belt as well.
If there is water all over the floor, there is probably a clogged drain as well.