* They are large, rigid pieces of the Earth's lithosphere. The lithosphere is the outermost layer of the Earth, consisting of the crust and the uppermost part of the mantle.

* They are constantly moving. This movement, driven by convection currents in the Earth's mantle, is known as plate tectonics.

* They interact at their boundaries. These interactions can be constructive (creating new crust), destructive (consuming old crust), or conservative (sliding past each other).

* They are responsible for many of the Earth's most dramatic geological features. These features include mountains, volcanoes, earthquakes, and ocean trenches.

It's important to remember that while the plates are rigid, they are not solid pieces of rock. They are more like a mosaic of smaller pieces that have been welded together over millions of years.