Crowns are a new feature that we believe lets us teach better. Each skill you do has a “Crown Level” associated with it. When you level up a skill, you earn a Crown, and the types of exercises you see will get harder. You can choose to go deeper into skills and level them up or continue on to new skills to learn new content.
This is a total redesign of the skill tree that solves one of Duolingo’s biggest challenges: remaining fun for casual learners while still offering advanced content for serious learners. Casual learners can still go through the whole tree fairly easily, while more advanced learners can get a lot more depth by leveling up their skills and earning Crowns.
You can think of Crowns as adding a new dimension to the course tree. Instead of just moving down the tree, you can now also move deeper into each skill. This allows us to give you more challenging exercises (like listening and typing in your learning language) when you're ready for it — and only if you want it.
We encourage you to check out the original post introducing Crowns for more details.