An inner circle is a small group of people who have something in common. It could be a group of friends, family members, or co-workers. The exclusive group can be a mixture of people as long as they have some of the same interests and goals.
It is amazing how many Christians say they do not know for sure what sin is. It is unfortunate that they sin and claim they did not know it was a sin. However, saying they don't know what sin is doesn't excuse them for sinning.