I'm a RYT-500!
What does this mean? Well, it means that I've taken a lot of yoga classes!
The Yoga Alliance is an association for yoga teachers and training schools. It outlines curriculum for trainings, sets a code of conduct, and is a registry for yoga teachers and schools. While it is not a certification to teach yoga, it does lend credibility and assures students that their teacher or studio is working within its guidelines.
After completing a 200 hour training, that new teacher is eligible to join the Yoga Alliance as a Registered Yoga Teacher 200 hour (RYT-200). From there, the RYT can level up to RYT-500 by completing another 300 hours in training. You may even see designations of E-RYT 200 or 500. These teachers have logged many, many hours of teaching and are thusly considered Experienced Registered Yoga Teachers.
Does this make one teacher better than another? No, not at all. There are some very talented and knowledgable teachers who choose to not register with the Yoga Alliance, as it is not a requirement to teach yoga. But it can give students some level of reassurance that their teacher has a well rounded education. I can honestly say that 200 hours is scratching the surface of all there is to know. The most important thing is that teachers and studios work in an ethical manner, keep their students safe, and make classes an enjoyable experience.