Chapter 4, "Auxiliary Organizational Structure," in the Auxiliary Manual (M16790.1F) provides an overview of Auxiliary organization.  Briefly, the structure is 

Coast Guard Auxiliary District 11 Northern Region (D11NR) covers Northern California, Nevada, and Utah and is composed of ten divisions and their flotillas.  Each flotilla has its own personality, but they all serve the boating public and support the Coast Guard through a variety of programs.  There is no geographical requirement regarding which flotilla an Auxiliarist joins, and Auxiliarists can work with other flotillas in addition to the one where they are a member. Flotillas are not attached to any particular Coast Guard station.

The flotilla is the local organization, and everyone must be a member of a flotilla.  Flotillas are numbered, and "Flotilla 12" means that it is Flotilla 2 in Division 1, while "Flotilla 11-3" is Flotilla 3 in Division 11.  The flotilla is led by an elected Flotilla Commander (FC) and a Vice Flotilla Commander (VFC).  Elected Auxiliarist leaders appoint staff officers who provide functional supervision and program management over specifically authorized activities. The Auxiliary is organized with similar staff officers at all levels. Staff officers are not barred from holding simultaneous elected offices or another staff office.  A staff officer's appointment expires with the term of the appointing leader. 

New Auxiliarists are not normally offered staff officer appointments during their first membership year. They can use this time to learn about the Coast Guard and to gain experience working with elected leaders or staff officers in areas of interest.

Flotilla staff officers (FSO-XX) positions are designated as:

The division is the next highest Auxiliary level.  A division has five or more flotillas in the same geographical area.  The division is led by an elected Division Captain (DCP). and a Vice Division Captain (VCP).  The DCP may appoint division staff officers who will be designated as SO-XX.

The Auxiliary district is the organizational unit above the division.  A district is headed by an elected District Commodore (DCO), a Vice Commodore (VCO) who serves as the District Chief of Staff, and one or more District Rear Commodores (RCO).  The DCO may appoint district staff officers (DSO-XX) and assistant district staff officers (ADSO-XX).  The Auxiliary district will coordinate with a Coast Guard district that has active duty officers assigned to this task.  At the district level, the geographic boundaries of the gold and silver sides are the same, but there is no geographic or organizational symmetry below the district.

Coast Guard Auxiliary District 11 North's Operations Page will give an idea of the many activities occurring in the district.