a force pushes or pulls it. a moving object will stay moving unless a force pushes or pulls it.
gravity and friction are forces that constantly push and pull the "stuff" on earth. so, when we roll a ball, it slowly comes to a stop. on the moon, where there is less gravity and friction, "stuff" floats, and keeps floating.
the items on the tablecloth - the drinking glasses full of water and the plate - are not moving. according to newton's law they should stay still unless a force pushes or pulls them. when you pull the tablecloth out from under them friction is a force that causes the plate to 