In Roblox, a Ray is a line that starts at one point and goes in a direction infinitely. Rays are most used with the FindPartOnRay method of the ExplorerImageIndex 19Workspace.

Ray Lua Object

Vector3 direction) Creates a new Ray at origin with a direction of direction
Vector3 Origin The start position of the Ray
Vector3 Direction The direction that the Ray is pointing
Number Distance(point) Returns the shortest distance from the ray to a point
Vector3 ClosestPoint(point) Returns the closest point on the Ray to the given point