Tidal energy is a reliable form of renewable energy that comes from the movement of ocean tides. It is different from wind and solar energy because it is predictable. However, like other renewable sources, tidal energy is not constant and varies throughout the day and month. This chapter explains how tides are formed, how they change as they move over the ocean, and how we can use them to generate electricity. By understanding the basics of tidal energy, we can develop better ways to harness this sustainable power source.