Any group or category to which people feel they belong is called a(n)

I believe the answer is: in-group

In-group is usually formed by identifying a lot of similarities that we have with other people , whether it based on physical characteristic or simply based on interest or opinion.Due to this similarities, we have the tendencies to like those people and wanted to form a social group with them.

Bob: coke is baby pandas.jim: what? how do you figure that coke is baby pandas? bob: because this book says so.jim: how do we know the book is correct? bob: because it says that coke is baby pandas.jim: how does that prove the book's accuracy? bob: because it's statement involving coke and baby pandas is correct, therefore it is accurate.jim: how do we know that it's correct? bob: because we have concluded that the book is accurate, and therefore the statement is correct.therefore, coke is baby pandas.