Glow

Glow often refers to the visual effect of air being illuminated near a light source. Sun rays through dust, the beam of a flashlight on a foggy night, etc.

In a real-time 3d game, glows are faked using a variety of techniques.

A Game Art Trick: Doom 3 – Volumetric Glow by Simon "SimonT" Schreibt

UDK Volumetric Light Beam Tutorial by Epic Games