You many have never even thought about this subject since when you are using a wide-angle lens it's hard to even find a place in the image where it's not in focus. That's the nature of wide-angle lenses, they always appear to be in focus from a few feet to infinity.
But Simon explains the fine points of focus using the hyper-focal distance of the lens and a second, more aesthetic based process.
The best way to track what Simon's real estate/interiors photography tutorials is to directly subscribe directly to his YouTube Channel. Be sure to click the Like button on the left hand site near the bottom of each video you watch... if you like it.