The horizon or skyline is an apparent line that separates earth from sky. The horizon is the line that divides all visible directions into the categories. Those that intersect the Earth's surface, and those that do not. In many areas, the horizon is obscured by trees, buildings, and mountains.
The resulting intersection of earth and sky is called the visible horizon. An example of the horizon is where the sky and earth appear to merge into one sea of blue. The point above the surface of the horizon appears to be slightly bent. It looks like a circle.