If a character is healed by someone with a proficiency in the Medicine skill and expends a use of a healer's kit, they receive a bonus equal to healer’s Medicine Bonus for each hit die healed this way. If there are no healer’s kits available, then the healer may attempt to heal the injured character after a DC 15 Medicine check, giving them a bonus of half the healer's Medicine Bonus (rounded down).
A short rest is a period of downtime, at least 10 minutes long, during which a character does nothing more strenuous than eating, drinking, reading, and tending to wounds.
A character can spend one or more Hit Dice at the end of a short rest, up to the character’s maximum number of Hit Dice, which is equal to the character’s level. Each Hit Die spent in this way takes 10 minutes to use, so a character who spends 3 hit dice will stop and take 30 minutes to treat their wounds.