What is the difference between a foothill and a mountain?

A foothill is a lower elevation landform that typically lies at the base of a mountain, serving as a transition between flat land and the steep slopes of the mountain. Mountains are significantly higher and steeper, characterized by their peaks and rugged terrain. Foothills often have gentler slopes and are usually less rugged than the mountains they support. Essentially, foothills serve as a buffer zone leading up to the more challenging terrain of mountains.