Filter thread. Lenses have a thread on the front for attaching filters and other add-ons. Some also use this thread for attaching a lens hood (you screw on the filter first, and then attach the hood to the screw thread on the front of the filter).
Lens hood bayonet. This is used to mount the lens hood for lenses that don’t use screw-mount hoods (the majority).
Zoom ring. Turn this ring to change the zoom setting.
Zoom scale. These markings on the lens show the current focal length selected.
Focus ring. This is the ring you turn when you manually focus the lens.
Distance scale. This is a readout that rotates in unison with the lens’ focus ...