This 24-page document is a great introduction to dressage concepts, published by Dressage Mastery Academy.
The document includes these topics and more
- Explanation of the German training scale
- Rider success scale
- What is Rhythm? How do I know if my horse is in Rhythm?
- What is Seat?
- What is Straightness?
- What is Impulsion?
- What should you expect from your horse?
- How to troubleshoot common problems at the walk, trot, and canter.
- Exercises to make your balance and movement better.
Print it out; talk it through with your trainer.
It gives a good explanation of the first goals for a new Dressage Rider.