Crash Course is a video channel you can access through YouTube. Crash Course Computer Science is an ongoing playlist of fast-moving videos that begin with the most basic underpinnings of digital computing and progress from there.
If you are a complete novice, you’ll probably want to take them one at a time, watch each several times, and perhaps also supplement them with other sources, to make sure you understand each new concept.
If you’re already somewhat familiar with the subject, this is a great review!