Bad Normals shows how you can create mountains procedurally using Geometry Nodes.
Typically you can use displacements and other tools to create mountains in 3D, which also holds with Blender. However, this tutorial from Bad Normals shows how you can build mountains procedurally using Blender’s Geometry Nodes.
Getting Started With Geometry Nodes.
Look no further for a simple introduction than this new tutorial from Remington Markham (SouthernShotty). Markam walks through what each node does, explaining a bit about how they each might be used. Later, as a practical example, he shows how to create a procedurally created environment with the new nodes.