A broad minded person is a person who is willing to accept types of behavior that other closed minded people do not accept.
For example a guy dresses up as a girl but a closed minded person would hate that and not accept that guy for who he is.
Another person who is broad minded would accept that person whether or not they think it's right.
Or if you have a parent that accepts you has being gay then your parent would be broad minded or open minded.
Broad minded and open minded people accept weird non natural or normal things that people do even though other people may not approve of it.