You magically twist space around you and another creature you can see within range. The target must succeed on a Constitution saving throw (the target can choose to fail), or the target is instantly teleported to the space you occupied when the spell was cast, while you instantaneously occupy the space the creature occupied when the spell was cast. 

The targets must be of a similar size and mass. For instance you can swap two medium sized creatures, or two items of a similar size, but you cannot swap a medium creature for a creature of a different size category, and you cannot swap objects that could not occupy the same space as each other.  You could not, for instance, swap a chair for a horse cart. You can swap objects for creatures and vice versa, so long as they are of a similar size and mass. You cannot swap large creatures, or objects weighing more than 1000lbs.