Landforms are the natural features of the Earth's surface, created by various geological processes like erosion, tectonic plate movement, and weathering.

Here's a breakdown of each:

* Plains: Large, flat areas of land with few changes in elevation. They are formed by the deposition of sediments over time.

* Mountains: Elevated landforms that rise significantly above their surroundings. They are formed by tectonic plate collisions that push up the Earth's crust.

* Valleys: Low areas of land between hills or mountains, often created by rivers or glaciers eroding the land.

So, plains, mountains, and valleys are all different types of landforms, each with unique characteristics and formation processes.