These are ordinary people who have no superpowers at all, only exceptional skills and abilities.
A natural is governed by the rules for Exceptional Abilities and normally cannot normally increase their attributes past 10. They also do not display any innate powers though they can have access to a few powers through gadgets.
Naturals commonly use Cyber, Fu, Guns, Items, Pulp, and Sorcery schticks. You can have a few Super schticks, but these must each have a special reason for their existence or come in the form of a Gadget.
By way of compensation for this, they get two free Pulp schticks; natural origin is considered to be worth two Pulp limitations.
Natural Supers in City of Heroes
Everyone is a natural by default; only by displaying unusual powers do you qualify for one of the other origins. This means that the vast majority of people in City of Heroes are natural. In order to achieve heroic status, you need special equipment and/or training, and this is usually provided by very well-organized and tight-knit groups.
The rank-and-file of many organizations are Natural by default, this includes most Longbow, Skulls and Hellions as well as low-ranking Council.
Crey
The rank-and-file in Crey is naturals. The Paragon Protectors are of science origin, and the Countess herself and a few of her henchmen are most likely mutants, but other than that Crey illustrates pretty well what can be achieved through training, dedication, organization, and mundane technology.
Family
The inner circle of the Verdandi family are Mutants, displaying an unusually stable strain of gravity powers. But the vast majority of the Family is natural; relying on their mundane gifts and weapons. The rebel Mooks of the Rogue Isles are all natural.
Malta and Sisters of Artemis
Pushing natural powers to the absolute limit, the Malta use their deep connections to use the city teleportation grid to their own advantage and manage to simulate many other super-powers through their gadgets. Still both the operatives or the technology are natural in origin; whatever super-tech they have is factory made.
Tsoo
The Tsoo use a lot of magic in their tattoos and to summon ancestor spirits, but their base power is martial arts and Fu.
Warriors
Masters of Melee Weapons, the warriors use raw skills and simple gear to achieve results.
Wyvern
Mantcore's henchmen are equipped with the latest in technology that they use when it serves their purposes, but the core of their power is their discipline, devotion, and archery skills.
Longbow
Though many of their leaders are mutants, and they use high-tech devices similar to those of the Malta group, Longbow define themselves by seal, organization and skill.