What is the primary characteristic that defines the position of Red Dwarfs on the H-R diagram?

Answer

They are both cool (low T) and small (low R)

Red Dwarfs are placed at the bottom right extremity of the main sequence band because they are characterized by having both low surface temperature and small physical size, resulting in minuscule overall energy output.

What is the primary characteristic that defines the position of Red Dwarfs on the H-R diagram?
temperaturestarastrophysicsdiagram