The NAAP HR Diagram Module explores the Hertzsprung-Russell diagram and those areas necessary to understand the diagram such as (but not limited to) the different kinds of spectrum, spectral classification, and luminosity class. In short, this module provides a fairly in-depth tutorial in reading HR diagrams.
First time users of NAAP materials should read the NAAP Modules – General Overview page.
HR Diagram Student Guide (pdf)
Take the pretest before reading the background material.