>>3553973the rangefinder is an optical device and it's mechanically linked to the lens focusing. a camera might or might not have it. disposables and cheap point'n'shoot cameras obviously don't have it, neither do p&s cameras with autofocus as they don't need it. the viewfinder on those is a plain window through which you see. it's not coupled to the lens or focusing.
pic related is a rangefinder. check out this site for a better explanation.
http://leicaphilia.com/how-a-rangefinder-works/ 