1. Mountains: These are elevated areas of land that rise significantly above their surroundings. They are often formed by tectonic plate collisions, volcanic activity, or erosion. Examples include the Himalayas, the Andes, and the Rocky Mountains.

2. Plains: These are vast, flat areas of land with little elevation change. They are often formed by deposition of sediment from rivers, glaciers, or wind. Examples include the Great Plains of North America, the Pampas of South America, and the Siberian Plain.

3. Plateaus: These are elevated, flat areas of land with steep sides. They are often formed by tectonic uplift or volcanic activity. Examples include the Colorado Plateau, the Deccan Plateau, and the Tibetan Plateau.

4. Valleys: These are elongated depressions in the Earth's surface that are often carved by rivers, glaciers, or erosion. They can be narrow and steep-sided, or wide and gentle. Examples include the Grand Canyon, the Yosemite Valley, and the Rift Valley.

It's worth noting that this is just a basic classification, and many other landforms exist, including hills, canyons, deserts, and islands.