Perspective, in context of vision and visual perception, is the way in which objects appear to the eye based on their spatial attributes, or their dimensions and the position of the eye relative to the objects. There are two main meanings of the term: linear perspective and aerial perspective
The Sun and the Moon appear to be roughly the same size because the Sun, although much, much larger, is also much farther away. The relationship between distance and apparent height of objects is not a linear pattern. If an object were actually touching the eye, thus being no distance away, it would appear infinitely tall.
Perspective is also seen in the way the parallel lines of how railway tracks appear to be meeting at a distant point (the vanishing point) on the horizon. When used in this sense, the 'horizon' is always at the level of the viewer's eye. Because the Earth is round, the true horizon (the line dividing the surface and the sky) is lower than this level. The difference is imperceptibly small when standing on the surface, but noticeable from great height (a person standing on a mountain can see further than someone at ground level). ''See horizon.
In graphic representation, an artist uses intuitive, artistic, scientific, or technical skills to represent the phenomenon of the visual perception of perspective. In simpler terms, these skills are used to add a suggestion of depth to what is ultimately a flat image or drawing. See Perspective (graphical).
Forced perspective can be used to deliberately misrepresent an object's size, making something appear larger or smaller than it really is. This is common in film, where a distant castle in the background may in fact only be a cardboard model a few feet high (and much closer to the camera). These are forms of optical illusions.