Absorption is how much damage is reduced by the armor or clothing worn by the victim.
Absorption is displayed in game as a single percentage, but works on per-hit, per location basis.
Each piece of armor reduces damage by a percentage not directly viewable. But, the amount of Absorption added to your overall stat is equal to the Absorption of that piece mutilplied by the about of hits each body location takes.
So, a chest piece that absorbed 90% of damage, would be mutiplied by the 49% of hits that go to the body, and increase the displayed absorption stat by 44% (really 44.1%, but partial percentages are not shown.)
Hit Percentage, by body part:
Head: 8% Body: 49% Arms: 14% Hands: 4% Legs: 20% Feet: 5%