Hilly terrain refers to land that has many hills, which are raised areas of ground. This type of landscape can vary in steepness and height, creating a series of ups and downs. Hilly areas are often found in regions like the Appalachian Mountains or the Cascades, where the natural processes of erosion and uplift have shaped the land over time. Hilly terrain can affect various activities, such as farming, construction, and transportation. The slopes can make it challenging to build roads or structures, while the elevation changes can influence local climate and vegetation. Many plants and animals are adapted to thrive in these diverse environments.