In this usage, Race is synonymous with species. All characters, whether player controlled or non-player characters (NPCs), have a Race. A Race in Super:Natural denotes a sapient creature capable of reasoning. Some examples would be humans, self-aware artificial intelligences and dragons. Not all races are necessarily intended for player characters as portraying an ancient dragon among a group of hobbits would be a bit unbalancing. Of course, it's your game, so you do what you want.
Each Race in Super:Natural has Racial Features that denote physiological function such as a natural ability to heal at an accelerated rate (Regeneration) or the ability to see in the dark. Racial Features may also be negative, such a particular sensitivity to sunlight or a weakness to fire. Racial Features are built in Advantages, Disadvantages, Powers and Weaknesses that are simply part of life as a member of a given Race. In many cases the benefits balance out with the drawbacks, such as a race that can regenerate but is weak to fire. Sometimes it may seem that there is no downside or, perhaps, that there is no advantage to playing as a human. That is up for you to decide.
Each Race in Super:Natural also has Racial Standards. These are oversimplifications of common features many, but not all, members of a given Race tend to exhibit. Racial Standards are intended as a guide for players new to role-playing games or who prefer following convention. These are intentional stereotypes of a given people that might simplify character creation. It is easy to say, "Oh, those elves... mages and rangers. All the bows and the spells." It may be true that an individual Valori might make for a great wizard or skilled ranger, but it might be equally true that a given Valori could be a talented chef, a singer with an angelic voice, or a backstabbing assassin. Any member of any Race is limited only by the availability of training and the technology level of their current planet.