Taking the model number "AF-S NIKKOR 18-55mm1:3.5-5.6G ED" as an example, I would like to explain:
AF-S: It refers to the autofocus lens that is suitable for DSLR cameras with AF-S size sensor. (It stands for having a lens ultrasonic focus motor for quieter and faster focusing)
NIKKOR: Brand name.
18-55mm: the lens is a zoom lens, the lens focal length equivalent to 35MM camera is 18MM ~ 55MM.
35mm camera: the reason why the camera is called 35mm camera is because the camera is used in the width of 35mm movie film. (The size of 35mm film is 36 x 24mm)
Later, this kind of movie film was sold exclusively in a dark box, called 135 film, so the 35mm camera is also called 135 camera.
1:3.5-5.6: The maximum aperture value of this lens is 1:3.5~1:5.6 That is, the maximum aperture value is F3.5 at the 18MM focal length, and the maximum aperture value is F5.6 at the 55MM focal length.
G: Lens motor-driven focusing, there is no manually-adjustable aperture ring.
ED: There are ED low dispersion lenses in the lens group.
The first type is a wide-angle lens. Wide-angle lens in this sense refers to the focal length of 35mm or less, such as 28mm, 24mm or even 16mm lens. Generally speaking, lenses under 24mm are called ultra-wide angle lenses. The focal length of the lens is multiplied by 1.5 or 1.6, so for this type of DSLR, a 16mm would be considered an ultra wide angle lens.
The second type is the standard lens. Generally speaking, the focal length is 50mm or 85mm. 50mm lens angle of view is the closest to the human eye, but only because of this, want to use a good standard lens is very difficult, because it is not like the ultra-wide-angle or macro lens, can shoot the human eye can not feel the picture. 85mm lens is generally a portrait lens.
The third type is the medium telephoto lens, generally 100mm or 135mm. 100mm of the lens is generally a macro lens, 135mm lens is also a portrait lens, but focus on half-body portraits, while the 85mm is more focused on full-body portraits.