What's a good website to search up the meaning of commands?

So this isn’t really about specific coding, but hear me out. I’m new to coding, and I’m basically relying entirely on YouTube tutorials. However, I want to actually learn what all the commands mean, not just copying them down. Is there a good website that has information on all commands, like a wiki almost? Where you could search up a command and they would tell you what it does, examples of it being used, etc. Any help would be appreciated!

Ye olde beginners guide: W3Schools.
Proper documentation: MDN.
Questions: Here.