If you'd some clarity, check out these tutorials from CCH (Wolters Kluwer CCH, a legal publisher): Tax Research: Understanding Sources of Tax Law (Why my IRC beats your Rev Proc!).
There are five lessons:
- Overview of Sources of Federal Tax Laws (13:33)
- Federal Statutes and Legislation (16:22)
- Treasury Regulations (14:06)
- Judicial System (12:02)
- IRS Rulings and Pronouncements (21:16)
It's easy to navigate within each lesson to hear about just the subtopic you need. Or you can read the accompanying PDF documents instead of listening to the narrator and watching the slides.
By the way, much of the material would be useful even if you aren't studying tax. For instance, most of the material about the federal legislative process is true of any federal law, not just tax laws. (Other laws go through different committees, not the House Ways and Means Committee and the Senate Finance Committee.)