Heal affects your ability to use healing kits.
Requires training: No
Check: Heal checks take place when using a healing kit. To remove a poison or a disease, the user of the healing kit must make a successful skill check against the DC of the affliction. The amount of hit points healed is equal to the modified skill roll. Healing kits often have "+1" or higher in their name, which indicates a bonus that will be added to your skill roll.
A character with a base heal skill of 4 and a wisdom score of 14 (+2) uses a healing kit +1 on himself. He rolls a 13 and thereby heals himself for 13+4+2+1 = 20 hit points.
Note: A character can always Take 20 when using a healing kit out of battle. Therefore, the character in the example above would heal for 20+4+2+1 = 27 hit points when not in combat.