I learned the very basics (cast on, bind off, knit, purl, knit 2 together, read a knitting pattern with those things in it) from my grandmother and a knitting book.

Nowadays, learning more about knitting is on a need-to-know basis. I'll see a pretty pattern and a technique in it I don't know, and decide that I'm willing to take on the project anyways. Or I'll reach the end of a project and realize I forgot the best way to weave in the ends and need to look it up.

When I end up needing to learn more, I'll use online resources, favoring articles with images (like this one telling you how to weave in ends in stockinette) and GIFs over videos, and favoring shorter videos over longer ones.