Most mountains form at plate boundaries, specifically where tectonic plates collide.

Here's a breakdown:

* Convergent Plate Boundaries: This is where two plates move towards each other.

* Continental-Continental Collision: When two continental plates collide, the immense pressure causes the land to buckle, fold, and uplift, creating mountain ranges. The Himalayas, the Alps, and the Appalachian Mountains are examples of mountains formed this way.

* Oceanic-Continental Collision: When an oceanic plate collides with a continental plate, the denser oceanic plate subducts (sinks) beneath the continental plate. This process can lead to volcanic activity and the creation of mountain ranges along the continental edge. The Andes Mountains in South America are a prime example.

Let me know if you'd like more details on any of these processes!