Start the washer and wait for the washer tub to fill with water. If you do not hear water or hear a motor whirring, the washer motor may be dead.
Open the washer lid in mid-cycle. Note whether or not the inner tub is still spinning around. The inner tub is the inside surface of the washing compartment with many holes for water draining. If the tub is not spinning but the motor is running, it is possible the pump is dead. Check the pump pulley by removing the pump from the washer and trying to rotate it by hand. If the pulley doesn't turn freely and is frozen or stiff, replace it. Also, if the agitator is moving but the tub isn't, this is a sign the pump is dying. For front-loading washers, do not attempt to open the door mid-cycle. Look through the glass door. If there is enough water to come up against the door, the pump is malfunctioning.
Wait for the washer to finish its cycle. Open the lid. If water is still in the tub, the pump is likely dying or dead.