Gaia Data Release 3 (GDR3) contains a wealth of information to advance our knowledge of stellar physics. In these lecture notes we introduce the data products from GDR3 that can be exploited by the stellar physics community. Then we visit different regions of the HR diagram, discuss the open scientific questions, and describe how GDR3 can help advance this particular topic. Specific regions include hot OB and A type stars, FGK main sequence, giants, and variable sources, low mass stars, and ultra-cool dwarfs. Examples of scientific exploitation are also provided. These lecture notes are accompanied by a 3-hour lecture presentation and a 3-hour practical session that are publicly available on the website of the Ecole Evry Schatzman 2023: Stellar physics with Gaia, https://ees2023.sciencesconf.org/, see Lectures and Hands-on Work.
O. L. Creevey (2025) studied this question.