What is raycast? use of it.

hii, anybody knows what is raycast, plz dnt provide me the unity raycast link, i just want explaination with simple example that i can try.

and use of raycast also......

A ray is a partially unbounded linear component, which is a fancy way of saying it's a line that starts at a point and continues infinitely in some direction. (Mathematically speaking, at least. In practice the ray may be bounded on the other end as well, in which case it's actually a segment test. In all cases however, the ray length will be limited by the range and precision of the underlying numerical representation.)

A 'ray cast' involves intersecting a ray with the objects in an environment. In other words, a ray cast tells you what objects in the environment the ray runs into, and may return additional information as well (such as the intersection point and normal).

Ray casting has many uses; for example, it can be used for line-of-sight tests or to determine what's 'in front of' an autonomous agent for AI purposes.

Like many other things, it'll become clear what ray casts are useful for once you find yourself in a situation where you need them. If you want more info though, just search UA and the forum archives for 'raycast', and you'll find plenty of information and examples.