Progress is saved every time you complete a module, watch a video, or read a document.
For SKILLS modules and mandatory videos, if you quit a halfway through, you will need to start again from the beginning next time. These must be completely finished in order for your progress to be saved. Your progress is not saved where you left off, so please have ample time before beginning a lesson.
You must have an internet connection in order for progress to be tracked. See Do I need to be connected to the internet to play?
See also: Review how Completion and Certification are different measures of your learning progression.