Polarized sunglasses cut glare and haze so your eyes are more comfortable and you can see better. Polarized lenses contain a special filter that blocks this type of intense reflected light, reducing glare.
CR-39 lenses, also know as plastic lenses, are one of the most common material for lenses. Plastic lenses became popular during the 1970s due to the fashion trend for large-sized frames. Plastic (also known as hard resin or CR-39) lenses are half the weight of glass lenses, which made them more comfortable. Plastic also provides excellent optics and vision correction. To overcome the softer lens surface, scratch resistant coatings are available and should always be recommended.
There is a large selection of lens styles that are available in plastic, which increases it versatility and usage. Although it lacks the built-in UVA/UVB blocking properties of other materials, plastics can be treated with UV protective coatings. Plastic also accepts tints easier than any other material.
The 'G' stands for 'Green' (there is also a brown 'B15' lens) , and the '15' relates to the amount of light transmitted through the lens - in this case 15% of visible light is transmitted, i.e. it blocks 85% of visible light. Note that this relates to visible light not UV - they will block 100% of harmful UV light.
Mirrored sunglasses are sunglasses with a reflective optical coating (called a mirror coating or flash coating) on the outside of the lenses to make them appear like small mirrors. The lenses typically give the wearer's vision a brown or grey tint.