Ned is a Scottish term that means "non-educated delinquent." Basically, neds are people who may not have had a lot of opportunities to go to school and learn important things, so they might act out in negative ways. They might wear certain clothes, use slang, and spend time causing trouble with their friends.
It is important to remember that just because someone is a ned it doesn't mean they are bad people. It just means they might make bad choices because they haven't had the same advantages as others. It is important to try to understand and help these people instead of judging them.