For the AF Nikkor 24-120mm 1:3.5-5.6D the rubber ring nearest the front of the lens is the focus ring. The numbers below it, which also move with the rubber ring, indicate focus distance. There are two scales, one in feet and one in meters.

The white line on the trim ring between the focus ring and the zoom ring is the index mark for both the distance scale above it and the focal length scale below it. The white line indicates the focus distance. The two dots to the left of the white line indicate the focus distance using infrared film when the lens is set at 50mm and 24mm, respectively. When the lens is set to other focal lengths, the focus distance can be approximately interpolated by the proportional distance between the 24mm dot, 50mm dot, and 120mm line.

When shooting infrared film (or using a modified digital camera to capture infrared instead of visible light) the distance between the 24mm dot and the 50mm dot where the focus distance is indicated for 35mm, for example, will be roughly proportional to the distance between the 35mm focal length mark and the 24mm and 50mm focal length marks on the zoom ring. So if the 35mm focal length mark on the zoom ring is lined up with the white line on the indexing ring, indicating the lens is currently zoomed to 35mm, then the current focus distance can be read from the focus ring at the point on the focus ring that is approximately halfway between the 24mm dot and the 50mm dot on the indexing ring, because the 35mm focal length mark is roughly halfway between the 24mm and 50mm marks on the zoom ring.

The widest rubber ring is the zoom ring which changes the focal length of the lens. The numbers immediately above give focal length in millimeters and the focal length at the current position will be lined up with the white indexing mark on the trim ring.

The rearmost and smallest ring (in diameter) is the aperture ring. The scale indicates the f-number of the lens. When the lens is at 24mm the f-number is indicated by the green dot. Notice that on the focal length scale 24mm is printed in green. When the lens is zoomed in to 120mm the f-number is indicated by the yellow dot. Note that on the focal length scale the 120mm mark is printed in yellow. When the lens is set at a focal length somewhere between 24mm and 120mm the f-number falls somewhere between the two dots in a similar proportion to the distance between the current focal length and the 24mm and 105mm marks on the focal length scale.

If the lens is being used on a camera that can automatically control the aperture, the aperture ring should be set at the minimum aperture size (f/22), marked in orange, and locked by sliding the lock switch just above the aperture ring so the white dot lines up with the orange line. The f-number selected by the camera can then be viewed in the camera's viewfinder or on the camera's display screen.

Here's a link to the AF Nikkor 24-120mm f/3.5-5.6D User Manual.