You conjure up an illusory wall in a location you can see within range. You can make the wall up to 40 feet long and 20 feet high. The wall has no depth and it vanishes when the spell ends. The wall is completely invisible and creatures can pass through it without any impediment. Any creature that looks through the wall can not see any creatures on the other side of the wall as if the creature was invisible. When you cast the spell, you can designate one or both sides of the wall to have this effect. 

A creature that uses its action to examine the wall can determine that it is an illusion with a successful Intelligence (Investigation) check against your spell save DC. If a creature discerns the illusion for what it is, the creature can see creatures on the other side.