A good clear example of the distinction can be found on Stack Exchange (source: https://english.stackexchange.com/questions/33443/what-is-the-difference-between-taking-courses-classes-or-lessons) :
Course is the broadest term for the study of a subject. It could be used to refer to an entire degree program, but it is most appropriately applied to a specific subject such as First Year English Literature.
Class list items more specific and is most properly applied to a section of a course taught by one instructor to one group of students at a certain scheduled time.
Lesson is the most specific and implies a particular unit of instruction, such as would be delivered by a particular instructor to a particular class on a given day.
There is also a difference between an instructional designer and a teacher/trainer/professor. The latter may create customized lessons, but may not design the overall course, which is what the former might do.
There are multiple styles of instructional design as well. I use a simplified version of the ADDIE model (https://www.instructionaldesign.org/models/addie/