Attention to detail could be a watchword for the design team at Outwell. Not content with the way that air-mattress valves work, they’ve designed a better one!
What you see above is a clever little 3-way valve system, with the middle position (as shown) being “inflate”.
When pushed to “Closed”, no air can flow in or out.
When pushed to “Inflate”, air can get in freely so the mattress can self-inflate (or be topped up by mouth.
When pushed to “Deflate”, air can be squeezed out, but can’t get back in, which means the process of rolling the mattress back up is easier, and you can take your hands/knees off it without it springing up and refilling with air.