In the first two sections of the book, you have learnt everything you need to know to be able to play great lead guitar by ear whether you read music well or not. However, if you want to be a good musician, it is necessary to learn all the notes on the fretboard and also know how to read them. This lesson covers some basic theory which you may or may not have already covered. If you already know the subjects covered here, read through them anyway, as they will prepare you well for the lessons to come.