A limited liability company is owned by its members, who may directly manage the limited liability company, or who may appoint managers to manage the limited liability company for them.
The members may also apportion duties amongst themselves as they see fit. They may even appoint one of their members to be an offficer (president, vice president, secretary, or treasurer) with the appointed member having the duties normally associated with such title or titles.
One of the virtues of a limited liability company is the ability (in most states) to structure the limited liability company in the matter which the members want it structured.