Let's start with USEF - the United States Equestrian Federation. USEF, started in 1917, is the national governing body for equestrian sports here in the USA. The USEF trains, selects, and funds our United States Equestrian Team and also licenses equestrian competitions of all levels across the United States each year. But what does USEF have to do with showing dressage? Competitors who wish to make it into the elite ranks must abide by all of USEF's rules. That means that if you hope to ride in the WEG, Pan-American Games, or the Olympics, you have to participate in events that are recognized by the USEF. Even if you don't plan on making any of these elite teams, others hope to, so even at the most beginner level shows, USEF's rules and expectations can be felt.
So on to the USDF - United States Dressage Federation, the only US national dressage membership organization. USDF's website states, Dedicated to education, the recognition of achievement and promotion of dressage, USDF is [an] organization with more than 30 different educational programs, 125 affiliate local or regional clubs and more than 2000 annual awards for excellence in competition. The national levels, Training Level through Fourth Level, are governed by the United States Equestrian Federation. The international levels are governed by the Federation Equestre Internationale (FEI).
USDF has approximately 125 local affiliates. These affiliate clubs are called Group Member Organizations (GMOs). By joining your local GMO, you automatically become a Group Member of USDF. Find your nearest GMO here. There are four different types of membership: Participating, Education, Group, and Business. Since each membership is slightly different, USDF recommends that you read about each membership carefully before joining.
There are are least four types of dressage shows in California. The first are simple schooling shows. Any type of judge may be used, even "L Graduates" from the USDF Education Program (not yet USEF licensed judges). Schooling shows can be quite formal and generally look and feel like a rated show. The exception is that riders can wear polos, times may run a bit wonky, and the general atmosphere is usually more relaxed. Many CDS chapters even put on non-rated series of schooling shows that have year end awards and prizes.
The next level of show in California is a CDS rated show. One-star shows, as they are called here, follow all USEF rules, but points are only earned for CDS championships or the Regional Adult Amateur Competition. One-star shows will have a licensed USEF judge, although they are frequently the lower level judges.
The third type of show in California is referred to as a three-star event, recognized by CDS, USDF, and USEF. These show usually have higher level judges and will often times attract more accomplished riders. Points are earned for national level awards as well as state awards.
The final type of show seen in California, or least the only other kind that I am aware of, are the CDI shows: Concours Dressage International, a dressage competition recognized by the FEI. CDI-W have World Cup qualifying or World Cup classes, while CDI-O have Olympic qualifying or Olympic classes. These are way, way, out of my league of course, but it's good to know what they are.
I haven't really cared how the shows are rated. There aren't very many shows close to me so I just go to whatever fits my schedule, whatever the rating. I've done a handful of schooling shows, a bigger number of one-star shows, and a few triple-rated shows. On Sunday I'm competing at a three-star event that is two and half hours north. I am not fazed by the recognition. I just want to show! In two weeks I plan to attend a local show that is another one-star event. Now that I hope to earn a CDS plate, schooling shows have lost their appeal, but this isn't a big deal since the only schooling shows I've found are more than two hours away.
So, still alphabet soup, or are things a little more clear?