What is the 'Learn' setting? What are important lines?
The "Learn" course option only exists for some special courses, like Dvoretsky's Endgame Manual - where there are especially denoted "important" variations. If you change this setting, you can either learn the whole content of the course, or make it so that the Learn Next button only takes you from lessons marked important to the next important lesson!
When our authors create their courses, our content team often asks them to create a Quickstarter guide so that users can quickly, as a first step, start playing the repertoire without having to learn every single line. Additionally they can also choose to mark a number of lines as important. This acts like a second step, i.e. users would first learn the quickstarter guide (let's say 40 variations) and then they could choose to learn the important lines only (this would be a larger number of variations, let's say 120 in a repertoire of several hundred variations). Only after that would they take the third step and learn all of the variations in the repertoire. Learning the Quickstarter is done by simply studying the first chapter of the course. To learn the important lines next, you would have to set 'Learn' to 'Important only'. Then, after you have completed doing that you would set 'Learn' to 'Everything' and study all variations.
In order for the 'Learn' option to show up at all, the authors have to mark variations as important. This is something only very few authors currently do, but we encourage this for all the new and large courses.
To swap between modes use the course options box (please see the image).
Swapping your learn setting is particularly important if you have already finished learning all the "important lines" and you want to complete the whole course instead.