Area which comes in cotact is more when an object is at rest than when it slides over a surface'frictional force is due to the presence of interlocking present on the surface of up and downs on the floor.sliding means draging an object along a floor.static means object is at rest. so sliding friction is less than static friction .but if the object have wheels it will be very easy to move it or rolls.then rolling friction<sliding friction<static friction