Read a textbook, or if the language of a textbook is too detailed for you to understand:
stars are born from gas clouds clumping together, they become more and more attracted to each other.
if they are heavy enough, all that energy of attraction (gravitational potential energy) becomes heat energy and starts nuclear fusion.
then they hop on to the Main Sequence of the H-R Diagram, their starting position depends on their mass from their birth.
they travel all the way down as they burn up nuclear fuel (hydrogen)
once they run outta nuclear fuel they hop onto the Red Giant of the H-R Diagram and if they're huge they go onto Supergiant of the H-R Diagram.
their death depends on their mass.
they can end up a white dwarf.
if they are heavier they end up a neutron star.
if they are EVEN heavier they become a black hole.
