Parhelia, commonly known as "sun dogs," are bright spots that appear on either side of the sun, often creating a halo effect. They occur due to the refraction of sunlight through ice crystals in the atmosphere, typically found in cirrus or cirrostratus clouds. These optical phenomena are most visible when the sun is low on the horizon, and they can appear as two bright spots at a distance of about 22 degrees from the sun. Parhelia are part of a broader category of atmospheric optics, which includes other effects like halos and rainbows.