Club admin is one of two sets of privileges that can be assigned to a user. The user needs to have role Coach or higher in one of the teams of the club to be able to become Club admin.
A Club admin has complete access to Club Settings. They can edit details of the club, assign or remove new Club admins and do user management over the entire club. If a user need to be moved from one team to another this is something the Club admin can do easily.
Apart from the above, Club admins also have the possibility to configure certain settings for multiple teams or even the entire club at once. Settings that can be applied to the entire club can usually be recognised by the Access setting on the forms.
Users that do not have Club admin privileges will instead see a list of athletes or other users to select when updating a setting.
You can learn more about managing Club admins here.