Going Over the Basics

A student put the following question out on Tumblr recently:

Small Child Playing Violin. Believed to be in Public Domain From Library of Congress, Prints and Photographs Collections.
From Library of Congress, Prints and Photographs Collections.

I’ve played violin for about 5 years but only in the school orchestra. Our teachers were never very good so I’m still kind of awful at understanding how keys and scales work and all fit together ( this is embarrassing omg) so basically I was wondering if you can think of any sources (preferably online) that go over all of the basics so I can review and finally understand what it is I’m playing? Thank you so much ūüôā

While there a numerous online resources for this (and others on Tumblr have mentioned a few, such as Teoria), if you want a paper book to work your way through, there are some good ones specifically for string instruments:

Either of the theory sets listed above will take you progressively through the basic steps and lead you to a good understanding of music theory. The note reading book is a good beginner book for reading music.