Area of Effect

From StarCraftWiki

Area of Effect is a general term for effects, spells or abilities that will affect an area, and the inhabitants of that area, rather than a single target. Also known as Splash Damage or Line Damage. Most attacks in StarCraft and StarCraft II will affect only one target, or only one target at a time, but some abilities such as Psionic Storm or Disease will affect all targets in the area.

It is not a given fact that the area of effect must effect all planes, it could just as well be that it only affects land, or only air. In most cases it affects both land and air.

In some cases, such as the StarCraft II Zerg Ultralisk or the Siege Tank, the unit will attack in a small area around the target, causing Splash Damage. Splash damage is the same as an Area of Effect, but generally only relates to a smaller area. In the case of Banelings, however, the area is quite large, but is still mostly referred to as "Splash Damage".

[edit] AoE Shapes

AoE effects can be of any shape or size, depending on the source. Many effects have circular AoE, but this is not a given rule. Some are also "Line Damage", and do damage in a square/elliptic shape with a width.