Understanding apertures for depth of field

Depth of field is how much of the photo is in focus. Aperture is an opening in the front of the camera using the blades. The shallowest depth of field would be f1.8 and the deepest depth of field would be f22. Stop down means to close the aperture to f22. You have to increase the aperture to make all 3 people in focus. The shutter speed would get slower as you increase the depth of field. In order to control the aperture you have to go to the aperture settings. A lense with a Big maximum aperture opening is a fast lense.