Answer:
Stars are born, grow up, and eventually die. The exact way that stars change as they age (or how they evolve) depends on how massive they are at birth.
Step-by-step explanation:
Stars are born when large gas clouds collapse under gravity. They form hot cores that gather more and more gas and dust until a protostar is formed. If only a small amount of gas is around, then only a small star will form; if a large amount of gas is present, then a massive star will form. Usually, the gas cloud is large enough for the cloud to break up into fragments so that multiple stars form of various sizes. The Sun formed from a very average sized gas cloud, and the bits left over stuck together under gravity to form the planets.