Damage Types (StarCraft)
In StarCraft, there are several damage types. The actual damage done depends on the type and the size of the target unit. All buildings are "Large" units.
Some attacks also do splash damage - enemy units near the target are also affected. These are usually (not always) powerful Normal or Explosive attacks. With the exception of the Siege Tank and the Infested Terran, splash damage does not affect your own units (but it will affect your allies' units).
However, if a unit is Shielded (Protoss units only), the shield takes full damage from any attack, regardless of the unit's size.
Damage type Size Concussion Normal Explosive Small 100% 100% 50% Medium 50% 100% 75% Large 25% 100% 100%