Potions

Potions are an in-game consumable that can be found as an uncommon drop on some enemies in SAO. As far as I know there are 2 forms of potions, but there may be more on floor 4.
Lesser Health Potion - They cost 100 col at any floor 1 shop but are worth 10x that price to a dying player. They will grant 200HP to any player who consumes it. Great for starter players, but you will need about 20 of them for higher leveled players.
Potent Health Potion - These potions cost 1000 col, grant 800HP, and are ideal for fighting boss enemies on higher floors. or just to sell top players on boss floors for more profit.
*Note - Lesser Health Potions can be dropped by enemies but cannot be dropped if you have one in your inventory already.