Courses are being offered by universities like Harvard and M.I.T. and by the teenager next door making videos in his garage. Where is the teenager next door po

Courses are being offered by universities like Harvard and M.I.T. and by the teenager next door making videos in his garage. Where is the teenager next door posting these videos? Just YouTube? Or is there a platform that lets independent teachers easily create courses with videos, assignments, tests, etc.?