How do we calculate or determine the distances to stars? What units do we use and what are the limitations (if any) of the method used for such calculations? 250 words

How do we calculate or determine the distances to stars? What units do we use and what are the limitations (if any) of the method used for such calculations? 250 words Discuss stellar evolution (describing each stage in brief). What forces are opposing one another throughout the life of a star and how do they influence the various stages in the life cycle of a star? 250 words