Here is Divine Lighting's Guide for Understanding Lighting Optics

What are lighting optics?

Optics in LED lighting can include the spatial distribution of light from the diode itself, and the reflectors, lenses, and holders that cut off or limit output light with mechanical blocking devices. Facilities that install LED lighting systems will use different optics in LED lighting, for example, to control the beam angle of the output light, to create either crisp-edged or diffused light, or to concentrate light in certain areas while limiting it in others.

For example, a sports arena will want to concentrate light onto playing surfaces to give athletes the best opportunity to see the fast action and fine details of the play that is progressing around them, without stray beams blinding spectators in the stands. Large outdoor parking lots will prefer lighting that illuminates the entire lot uniformly, with no dark areas or shadows that might make motorists uncomfortable. The specific application will therefore define the optics that will go into the application’s lighting system.