Khan Academy started out as a YouTube channel, so there are a lot of instructional videos that come along with the lessons, which provides a nice variety of learning mediums.
Khan Academy is a massive non-profit educational tool covering subjects from math and science to history, even language arts! They provide self-contained lessons that you can interact with right on their website. When learning how to code for example, you will write and test the code all on Khan Academy's website. Khan Academy started out as a YouTube channel, so there are a lot of instructional videos that come along with the lessons, which provides a nice variety of learning mediums. This is a great resource for students of all ages, but definitely designed for serious learners.