Your health influences the damage your weapons deal in the last stand. As you suffer more and more damage, the power of your attacks will grow more and more powerful against your enemies.
On success you get 10.5 health pool for 44.2 rounds.
Abilities are associated with one or more classes and can be used by both players and NPCs, and most abilities has to be learned and sometimes require points to be invested into them. Rarely, you can find a special ability scroll with limited uses, and these can be used if you have not learned the ability, but with a limited number of uses on the scroll.