When I started using THREE.js, I did not had any previous encounters with it. I learned it just from using the docs. Asking your question: you should look at the tutorials / examples given in the docs
You can also find every class / member + some explanation in the docs too. Many beginners do not know how to read it, so they need stuff like Youtube videos. If you find yourself in that category, I recommend you to learn how to read the docs in the first place, you won’t find it worthy until you learn it. Most docs for any given lib is following kinda the same structure
It used to help me as a beginner to vary basic examples and learn through that. Of course, with the help of the available documentation.
Since there are many useful small examples published here in the forum I have compiled them in the Collection of examples from discourse.threejs.org .
Note that three.js is constantly changing. You should start with the 2021 vintage. See the beginner example in the collection and read the docs that can be found at the bottom of the page * discourse.threejs.hofk.de .
The official examples are often very complex and for the beginner it is hard to pick out a single thing.