Which door type slides into a slot inside the wall?

The correct choice, which describes a door type that slides into a slot inside the wall, is indeed the pocket door. Pocket doors are specifically designed to save space and provide a clean look by retracting fully into the wall when opened. This allows for unobstructed access to the area beyond the door, making them particularly useful in smaller rooms or spaces where a traditional swinging door would be cumbersome or impractical.

In contrast, swing doors require a clear area to open outward or inward, which can limit accessibility. French doors also swing open and typically operate on hinges, offering a different aesthetic and functional use in spaces, usually providing a visual connection between rooms or to the outside. Sliding doors, while they do move laterally, typically slide along a track along the wall's surface and do not recess into the wall itself.

Therefore, the unique function and design of the pocket door set it apart, making it the most suitable answer to the question regarding a door that slides into a wall slot.