What do the green check marks in the lessons and locked courses mean?

What do the green check marks in the lessons and locked courses mean?

1. A green check mark shows that a lesson is complete.

2. Typesy recommends completing lessons in order: Level 1 > Level 2 > Level 3, and so on. If you click on a lesson out of sequence, a "Course Locked" prompt will appear. If you'd still like to skip, you’ll see the option to Skip Ahead and begin the selected lesson.