A camera that has a rangefinder which allows you to judge the focusing distance is called a rangefinder camera. A rangefinder is an optical contraption which enables distance to be estimated or measured by using such methods as triangulation, laser and radar. A rangefinder will show a double image. It will then align the images of the object being focused on and gauges its distance.
Some older style cameras will display the distance and you have to transfer it to the lens focusing ring. Newer models are coupled rangefinders. Which means the focus is adjusted in the rangefinder and the lens by the same control mechanism, which is usually a ring on the lens. The rangefinder is also separate from the viewfinder in some older cameras. However in most newer models the rangefinder is found in the center of the viewfinder. These cameras were popular from the 1930s to 1970s and most press cameras were rangefinders.
Some rangefinder cameras use 35mm film, have focal plane shutters and interchangeable lenses, while others have fixed lenses and leaf shutters. Digital rangefinders are also available. They range in price from about $500 to over $10,000.