A horizon, also known as the apparent horizon, is the line where the sky seems to meet the ground. There are several synonyms for this term, including the visible horizon, the eye-level horizon, and the distance line. It can be described as the point of terrestrial observation or the limit of perception. The horizon can also be used metaphorically to refer to the limit of one's knowledge or understanding. Other terms used to describe the horizon include the skyline and the vista. Regardless of the specific terminology used, the horizon remains an essential aspect of our perception of the world around us, providing a sense of depth and perspective to our surroundings.