True doubles are stars so close that they actually orbit each other. Optical doubles are distant stars that are visually aligned so they appear close, but they are independent systems and do not orbit each other.
Pairs are bright stars that happen to be fairly close. Pairs also do not orbit each other, they just happen to appear in the same field of view. Which stars are considered pairs is very subjective. For inclusion in this gallery, a pair is considered to be any two or more bright stars that show up in the same photographic field.
Multiples are orbital systems that contain more than one star. This includes true double stars as well as systems containing three or more stars. The majority of star systems, perhaps sixty percent or so, are part of a multiple star system. Our sun, being a solitary star, is therefore in the minority.