Nomads
Origin
The people that couln't accept the rule of the Raiders and ran away as a result of their terrorism became known as the Nomads. The Raiders went after them immediately and caught most of them. Even most of the ones they couldn't catch didn't make it very far. They either died to wildlife, hunger or even radiation in the early days. But some of them made it. No one really knows much about those few, not even how many they actually are. All that is known is that sometimes a Nomad makes it to a village and tells about his people. This is the only information available anymore and very few Nomads came anywhere near a village in the last 20 years, though some have been caught and executed.
Society
Nomads are very diverse group of people. They mostly live in groups of up to 10 people, sometimes family, sometimes friends, sometimes strangers, and roam around the world trying to survive. One thing they have in common is that they all have special skills. Be it survival, stealth or physical strength, the people that made it as Nomads have something that differentiates them from ordinary people. There have been reports of groups of Nomads that were trying to grow in numbers and fight the Raiders, but since the Raiders control everything this is unlikely, and some Settlers might just believe this story because they want to. There are also stories about a group of Nomads that tried to collect as much knowledge from the old world and store it at a safe place, so it won't get lost. This group most likely at least existed at some point as the Raiders have caught one of them trying to save some books they were about to burn, but how much this group has actually collected or even if it exists anymore isn't known. Other Nomad groups just want to survive without getting caught by Raiders and stay away as far as possible from any Raiders and, as a result, villages, so knowledge about them is very limited. The last groups of Nomads are the ones most Settlers and Raiders are familiar with. They are the ones that try to help the villages and kill as many Raiders as possible. Over the years these groups have quieted down after many of them got caught and it seemed like they lost hope or just stopped caring. But the settlers still believe they haven't died out and more of them will come back one day.