Shooting glasses, like safety glasses, are defined by their lenses, frames and fit. It is these characteristics that make them unique and specifically designed for the purpose you intend, whether that's skeet shooting or operating a chainsaw.
Lenses are designed to be impact-resistant in both cases because of the recoil and ricochet hazards involved in shooting as well as the presence of sawdust, metal filings or other hazards in industrial applications. Lens materials vary from crown glass and CR39 plastic to polycarbonate. Polycarbonate is the best material by far because of its higher impact-resistance rating. Prescription lenses are offered with some safety and shooting glasses.
Neither crown glass or CR39 plastic offer UV protection, while polycarbonate does. Both shooting glasses and safety glasses are available with a variety of lens colors designed for indoor and outdoor use, as well as for different degrees of light.
Early shooting frames were typically an aviator design but have evolved to include greater eye coverage, including wraparound eye coverage. Safety glasses also have evolved from the goggle effect to more stylish, wraparound designs virtually indistinguishable from fashion eyewear. Frames are made out of different materials, ranging from plastic to the preferred titanium or aluminum in high-end shooting glasses. The latter are much lighter material.
Proper fit is extremely important for either safety or shooting glasses. Ideally, look for rubber temple pads that are nonslip and sweat resistant. These will help keep your glasses on your face when exerting yourself. Also, look for rubber grips at the temple or ones designed to wrap around the ears. Both of these will help secure your glasses during strenuous activity.