The stars are born in clouds of gas called  nebulae, like the one we see on the left. Its matter condenses and heats up until a group of stars is born from the same cloud. 

Our sun was born, probably together with other suns, about 5000 million years ago in a cloud similar to this one and it will continue to shine for many more millions of years. 

When there is no more hydrogen left in the nucleus, the stars like the sun lose their outer part as in the photograph on the right, and shrink to small and very dense bodies called white dwarfs (can you see it in the centre of the cloud?).

 What do the differences from one to another depend on? To find out click on Star