Skeletar muscle moves a skeleton super simple, simply by that contraction. Smooth muscle lines our hollow organs and so things like the digestive tra line. It's similar to putting a tennis ball in a stocking and then using your hand to squeeze that tennis ball up the stocking. And this is how we push vecal material through a digestive tract, push urine out of he tennis ball bladder with my hands andnd a pair of stockings. It's all because of this smooth muscle layer.