Hitsplat

Hit-splat (also commonly known as Hitsplat or Hit splat) is a term used to refer to the damage icon appearing above a player, an NPC, or a monster, while in combat. A hit-splat usually results in the reduction of life points. A splat of disease doesn't result in a loss of life points but a loss of skill points.

Types of hit-splat
The colour of the hit-splat usually gives an indication of the type of damage and the number inside the amount of damage dealt.