I wouldnt say best. But its probably the most useful.
YouTube is the most valuable instructional tool around. People go to college for years to learn things that YouTube imparts for free. Average joes can learn how to fix their own cars, survive in the wild, provide emergency life saving medical aid, and the list goes on. Teachers and professors even stream over it.
You can learn enough about something from the comfort of your own home, to actually make a career out of it, which is crazy.