The geographical horizon refers to the line where the Earth's surface and the sky appear to meet. It is the limit of what can be seen from a specific viewpoint, influenced by the observer's height and the terrain. For example, standing on a flat plain provides a different horizon than being on a mountain. Factors such as topography, weather conditions, and atmospheric refraction can affect how far one can see. The horizon is crucial in navigation and understanding the layout of the land, as it helps determine distances and the visibility of landmarks like mountains or buildings.