Muscle cells, also referred to as myocytes, are cells in our bodies (and all other animals too!) that are responsible for movement.

The muscle cells work by contracting and relaxing over and over by using energy. Some are involuntary (contract/relax on their own), some are voluntary (you have to think about it to do it).

There are three types of muscle cells:
skeletal, cardiac, and smooth.

Skeletal might be the first type of muscle you'd imagine - think biceps, calf muscles. Cardiac cells make up your heart. And smooth muscle cells are part of internal hollow organs that need to move and push things along, like your stomach. I hope that helps!