Humans use the same process that stars use. Humans use it to make electricity, and stars use it to shine. This process is called nuclear reaction. Imagine the core of a star. Inside, a giant thermonuclear reaction is taking place. The nuclear reactions that happen in stars can last for billions of years.
A star is made in a huge cocoon of dust grains, gas, and molecules. The gas starts to get smaller, and the temperature rises. When the temperature reaches about 1,800,000º F. a nuclear reaction starts. The end of a star's life is marked when the star runs out of fuel for it's nuclear reaction.