The difference between an exercise and a lesson

An exercise is a fixed item in the syllabus, a thing the course requires the student to learn. A lesson is a flight that actually happened, in which you covered one or more exercises and graded them. The exercise is the plan; the lesson is the event.

Why they are separate

A syllabus lists its exercises in order, with the rules for completing each. That list is the same for every student on that version of the course, it is the standard.

A lesson is what you flew today. One lesson often covers several exercises, and a single exercise is often revisited across several lessons before it is signed off. Keeping the two separate lets a real training day, which rarely maps one-to-one onto the syllabus, be recorded truthfully.

Grading and sign-off

In a lesson you grade the exercises you covered and sign the record. The grade attaches to the exercise for that student; the signature attaches to the lesson. An exercise counts as complete when it has been graded to the standard the syllabus requires, not simply because a lesson mentioning it took place.

What this gives you

Because progress is measured at the exercise level, a student's position in the course is always clear: which exercises are complete, which are in progress, and what stands between them and a recommendation. That view is assembled from the lessons you have already recorded, you do not maintain it separately.