Source: Player's Handbook
You gain the following benefits.
Enhanced Unarmed Strike. When you hit with your Unarmed Strike and deal damage,
you can deal
Damage Rerolls. Whenever you roll a damage die for your Unarmed Strike, you can
reroll the die if it rolls a 1
Improvised Weaponry. You have proficiency with improvised weapons.
Push. When you hit a creature with an Unarmed Strike as part of the Attack action on your turn, you can deal damage to the target and also push it 5 feet away from you. You can use this benefit only once per turn.