A low bay light is typically used with ceiling heights 20’ or less. High bay lights are typically used when ceiling heights are 20-45’ high.
Most notably, a low bay light usually features some type of diffuser on the bottom of the light to spread the light in a manner reflective of the lower ceiling height. High bay lights typically have an aluminum reflector which allows a beam of light to reflect downwards to the floor area. Other types of high bay lights have a prismatic reflector which illuminates shelving, etc. from the floor to the ceiling.
Whether you are using low bay lights or high bay lights, metal halide type lighting overwhelming allows users to illuminate large areas with very few lights, making it the energy savings choice for buildings of all sizes.