A German window usually opens in two ways with one handle. In one position the window tilts open at the top. In the other it swings open like a door. A gear turns the movement of the handle into the straight movement of rods.
A lock prevents a wrong move, the Fehlbedienungssperre. It stops the handle from going straight from the tilt position to the turn position. Tilt-and-turn fittings are still the most common choice in German housing and commercial building.