Sneak Attack (Melee) is a Rogue Action. This ability allows the Rogue to exploit enemies' distraction and deal extra damage to their vulnerable spots with Melee Weapons.
The weapon has to have the Finesse property (but can still utilize Strength if it is higher than Dexterity).
Deal an extra 1d6 damage to a foe you have Advantage against. You can also use Sneak Attack if you have an ally within 1.5m / 5ft of the target and you don't have Disadvantage.