DSLRs have a separate sensor up near the viewfinder that does phase detect autofocus, this is different in that it can determine how far the lens is from being in focus and go directly there which makes it significantly faster which was crucial in many professional applications.

Please someone tell my D7500 this. I’m genuinely not sure if it’s the camera or my shitty glass, but I have regularly completely missed shots because the camera refuses to focus properly, but also refuses to actually shoot while it’s not in focus.