Our Sun is a medium sized star. It uses Hydrogen as its basic fuel to keep burning. Every second sun uses 6 million tons of Hydrogen.
But about 5 billion years later from now it will run out of its fuel, due to which it will become a giant red star and soon after it will start expanding. As a result Earth will receive more light and get warmer and warmer. Oceans will evaporate and most of life will die.
In about 7 billion years, Earth will become a burning planet. But the Sun has not finished yet. With time it will start expending faster and consume Mercury and Venus. Finally, probably it will consume entire Earth. That is how story of our beautiful planet Earth will end.
Finally the Sun will collapse into itself and end up as a white dwarf until it runs out of every bit of remaining fuel.
*run out of を使い果たす
*white dwarf 白色矮星