You gain a +3 bonus to attack rolls and damage rolls made with this magic weapon.
The first time you attack with the weapon on each of your turns, you can transfer some or all of the weapon's bonus to your Armor Class. For example, you could reduce the bonus to your attack rolls and damage rolls to +1 and gain a +2 bonus to Armor Class. The adjusted bonuses remain in effect until the start of your next turn, although you must hold the weapon to gain a bonus to AC from it.
When you take the Attack action on your turn and attack with a Light weapon, you can make one extra attack as a Bonus Action later on the same turn. That extra attack must be made with a different Light weapon, and you don't add your ability modifier to the extra attack's damage unless that modifier is negative. For example, you can attack with a Shortsword in one hand and a Dagger in the other using the Attack action and a Bonus Action, but you don't add your Strength or Dexterity modifier to the damage roll of the Bonus Action unless that modifier is negative.
If you hit a creature with this weapon and deal damage to it, you can reduce its Speed by 10 feet until the start of your next turn. If the creature is hit more than once by weapons that have this property, the Speed reduction doesn't exceed 10 feet.