Janus is a special type of door that can open in two directions, like a gate that you can push and pull. It's named after a Roman god who had two faces, one looking forwards and one looking backwards.
The idea behind a Janus door is that it can help people move in and out of a room or building more easily. For example, if you were carrying a big box into your house and your hands were full, you could just push the door open with your foot to get in, and then pull it closed behind you. Then, on your way out, you could use your hand to pull the door towards you and walk right through, without having to put the box down or juggle it around.
Janus doors are often used in public buildings, hospitals, and other places where people might need to move quickly back and forth without obstruction. They're also sometimes used in residential settings, like a pantry or closet with limited space, where a regular door might be in the way.
So the next time you see a door that swings both ways, you can imagine yourself as the mighty god Janus, overseeing all who pass through!