When you select a course you go directly to the course view mode and have the option to start it (if it’s the first time you open it) or resume from the last seen unit.
A progress bar in the “Content” block displays your overall progress within the course.
You can complete a course/lesson’s “units” via various actions; including clicking on a “complete course” button, answering a question or spending a minimum elapsed time. Depending on the traversal rules set for course might necessitate to complete units in a serial order. Each course has a course completion rule (e.g., complete a specific test or complete all units). When you complete a course a popup will appear with your options for the next step, which may include proceeding to the next course or download a certification