It is how far away the thing you focused on is. It is the one dial that does not change what the picture looks like on its own. It only decides where the sharp zone sits.
A note on where it is measured from. This tool measures from the lens, which is the standard form of the depth-of-field equations. Your camera body prints a focal-plane mark and manufacturers quote closest-focus distances from THAT, so a published minimum focus distance is about one focal length longer than the number here. At normal working distances the difference is small; up close on a long lens it is not, and neither this model nor any simple one accounts for focus breathing, which is a real zoom changing its actual focal length as it focuses near.
Think of the sharp zone as a slab of glass floating in front of you. Aperture and focal length set how THICK that slab is. Focus distance slides the whole slab nearer or further. Everything inside it is sharp, everything outside is not.
In a portrait you park the slab on the eye. In a room you park it at the hyperfocal distance, because that is the one position where the back of the slab reaches infinity.
The dial will not let you go closer than the lens can physically focus, which is why the floor moves when you zoom.
Focus on something 3ft away and you get a little sharpness in front of it and a little behind. Focus further out and that zone grows, and it grows faster behind than in front.
Keep going and you reach one exact distance where the far edge of the zone lands on infinity. That distance is the hyperfocal distance, and focusing there gives you the biggest sharp zone that lens and aperture can produce: everything from half that distance all the way out.
So yes, there is a sweet spot, and it is exactly one number. Focus nearer than it and the back of the room goes soft. Focus further than it and you keep infinity but throw away foreground for nothing, because infinity is already as far as far goes.
It shrinks fast as you go wider and as you stop down. At 17mm and f/8 it is about 4ft, so that lens focused 4ft away is sharp from 2ft to the horizon. That is why wide glass owns interiors, and why a stadium and a bedroom take almost the same settings. It is also why scale shots rarely need f/16: at 17mm you have usually won by f/5.6, and past f/11 diffraction starts taking sharpness back.