You create a sword-shaped plane of force that hovers within range. It lasts for the duration.
When the sword appears, you make a melee spell attack against a target of your choice within 5 feet of the sword. On a hit, the target takes 3d10 force damage. Until the spell ends, you can use a bonus action on each of your turns to move the sword up to 20 feet to a spot you can see and repeat this attack against the same target or a different one.
You can find more information on this spell in: PHB.262