Fold mountains are basically formed as a result of

Fold mountains are formed as a result of compressional forces. When two tectonic plates collide, the rock layers between them are pushed together and forced upward, causing the crust to fold and buckle. This process is known as orogeny and it results in the formation of fold mountains, such as the Himalayas, the Alps, and the Andes. The compressional forces can also cause the rocks to fracture and fault, leading to the formation of thrust faults and overthrusts. Over millions of years, erosion can wear down the mountains, but the forces that created them can still be seen in their folded and faulted rock layers.