Main sequence

What is the main sequence? What is the basic property of a star that determines where it is located on the main sequence? Are there stars that do not lie on the main sequence and, if not, why?     Main sequence is a band of stars spanning the H-R diagram. It runs from the top left of the diagram to the bottom right. The main sequence is divided into upper and lower parts, based on the dominant process that a star uses to generate energy.     About 90 percent of the stars are within Main Sequence. The radius, luminosity and temperature determine where the stars are located on the main sequence.     Red giants and white dwarfs are not located within the main sequence. Red giants are mostly shown in the upper right corner of the H-R diagram and the white dwarfs are mostly shown in the lower left corner of the H-R diagram. The white Dwarf and the Red giants counts only 10 percent (9% white dwarfs and 1% red giants) of the total stars.