draws on the body's natural healing ability to cure your wounds.
Potions of healing are basic potions that restore Hit points based on an amount separate from your healing surge value. It takes a healing surge to use them so it is usually a good idea to use them when it restores more than your current healing surge value.
Drinking the potion consumes it and is a minor action.
Potions can also be useful when you need a way to heal yourself in combat and other methods are unavailable or exhausted (second wind, party healer, etc).
Gaining more HP than you would with a second wind or other healing source, if the potion heals more than your normal surge value. Lower-HP characters like wizards and rogues may see this benefit more often than do high-HP characters like fighters, and they will also have fewer surges to spend.
Most characters' second wind is a standard action. Because using a potion is only a minor action, it can allow the character to do emergency healing without forfeiting their attack or other standard action choices that turn. The character could, for example, heal with both his second wind and with a potion.