Years ago when I was learned not only the guitar but music theory in general thanks to the internet since I have no teacher, I made this document compiling what's a note (in a musicwise not physical/wave stuff), how to make a scale or a chord.

It's a short document that I go back sometimes but my questions are : 
Could that be useful to anyone ?
Should I do something with it else than letting it sit somewhere on my google drive ?
And most importantly, is there any big mistake in there ?

Thanks for the feedback