The material you're using to learn has two levels: the concepts it tries to explain, and the concepts used to explain them. For the material to be truly useful

The material you're using to learn has two levels: the concepts it tries to explain, and the concepts used to explain them. For the material to be truly useful you already need to have an understanding of the latter. Some learning, of course, is by example/exposure rather than by explanation, otherwise you'd never be able to even get started.