Angels are mortals of any species who have died and since passed on to Heaven. They are easily recognizable by their halos floating over their heads and the feathered wings that sprout out of their backs. Most angels live peacefully in the afterlife, although a few volunteer to become warrior angels.
All angels are equal in the sense that they are just souls, but none the less they are divided into different classes based on their role in Heaven society. These roles are displayed through an angel's halo (via color and decoration) and in some cases also grant them special abilities.
As the title implies, common angels make up the majority of Heaven's population. The term applies to anyone who isn't assigned to one of the specialized classes. Common angels do not belong to any specific occupation - They can be anything from workers, business owners, teachers, independent scientists, artists, to angels who have simply chosen to retire instead of spending their afterlife working. Common angels have a golden, metallic halo.
Specialized angel classes
Angels who have just made it into Heaven are given a grey, metallic halo. This halo has no powers apart from letting the angel grow wings. With no ability to cross dimensions, the new angels depend on a guardian angel to take them where they need to go. This restriction mostly exists for people's own safety - It would be very unfortunate for an angel who has not yet learned how their halo works, to accidentally teleport themselves somewhere without being able to figure out how to get back.
Despite their name, the arch angels aren't really angels at all. They are deities who existed long before any souls were around and still rule over Heaven to this day.