What is Hertzsprung–Russell Diagram?

Main objective of this lecture is to present on what is Hertzsprung–Russell Diagram. H–R Diagram uses surface temperature of the star and the absolute magnitude (brightness) of the star to help astronomers decide which phase of the star’s life cycle the star is in and other important information about the star.  Hertzsprung presented his information in 1905 in the form of tables, while Russell presented his observations in table form in 1913. Today the diagram is named for both men’s work in correlating a star’s brightness and surface temperature.