Absorb is a very useful ability that eases the need to meditate or be healed. Attached to weapons and equipement (for example Wan Daye Weapons, this ability takes the amount of damage you do and gives you a certain amount of Life or Vital Energy, depending on the strength of the absorb, and the overall damage you can do. Shown below is a mathematical example for further clarification.
If I have an absorb ability that absorbs 3/1000 damage into Life, the following will occur whenever I attack something (independent of whether it is a PvP or PvE situation).
The attack succeeds and 4000 damage is dealt to your enemy. Following this, I will gain 4000/1000 x 3 Life back (12 HP). While this may seem small per hit, while grinding the difference adds up, especially when one has to deal 50,000 damage to a mob to kill it (following this logic, the player will get back 150HP PER mob, a large amount of HP).
The advantages of this are obvious - if you can do enough damage, the time in-between meditations or heals increases which prolongs grind time and thus, levels you quicker.