What basic function do contour lines serve on a map?

Contour lines on a map serve the essential function of showing elevation changes across the terrain. By connecting points of equal elevation, these lines allow map readers to visualize the topography of the area. The spacing of the contour lines also provides important information about the steepness of the slopes; closer lines indicate a steeper incline, while wider spacing suggests a gentler slope. This representation is vital for activities such as hiking, land development, and understanding how the landscape changes.

While maps may include other features such as water bodies, population density, or national boundaries, those aspects are typically represented through different symbols or color gradients rather than contour lines, which specifically denote the vertical relief of the land.