The members of a flex family form an asset inheritance tree, where child assets inherit various attributes from their parents.
As a content provider, you will not directly work with all of the members of the flex family. In fact, you will mainly be working with flex assets, which are the key members of flex families (all of the other members of a flex family contribute to the flex asset in some way). If you have the appropriate permissions, you may also be responsible for creating new flex attributes, which are characteristics of flex assets.