Some doors have no latch-handle on one side requiring a key to be used to retract the latch.

The question. If you leave the house, with the door unlocked, and decide to re-enter the house without having the key, then how will you open the door? With a classical door, you rotate a moving handle. But with these, the handle doesn't seem to be rotateable.

In such a case the door would also be unlatched, hopefully held open with a door-stop to prevent wind from slamming it.

Some doors have no latch-handle on one side requiring a key to be used to retract the latch.

The question. If you leave the house, with the door unlocked, and decide to re-enter the house without having the key, then how will you open the door? With a classical door, you rotate a moving handle. But with these, the handle doesn't seem to be rotateable.

If you latched the door behind you then you are out of luck and need to call someone on the inside, find a (person with a) back-up key or call a locksmith. With a door like that you should have the habit of always having your keys with you to avoid that scenario.

If you want to leave the house without a key and reenter later then you need to prop open the door with a door-stop to prevent wind from slamming it. Sometimes you can leave the door resting against the latch but a strong draft can still overcome that resistance and latch it closed.