What is focal length?
A lens' focal length, measured in millimeters, is the distance between the point where light rays converge and the digital sensor, also known as the focal plane.
The focal length of a lens corresponds to its angle of view, which tells us how much of the picture will be recorded, as well as its magnification.
If the focal length is longer, the angle of view get narrower and the magnification gets higher. If the focal length is shorter, the angle of view gets wider and the magnification will be lower.
Camera lenses with long focal length are used to shoot objects that are further away. Because there is a lot of magnification and a narrow angle of view, it does make objects in the distance appear larger.
Camera lenses with short focal length, are called wide angle lenses. They are often used to film large spaces because there is not a lot of magnification and it has a wide angle view. Perfect for filming real estate footage for example.