The smallest star in the universe is called EBLM J0555-57Ab. It is about the size of Saturn, and it is located about 600 light years from Earth. Our sun is much larger than EBLM J0555-57Ab, with a diameter of about 1,392,000 kilometers.
Stars form when large clouds of gas and dust collapse under their own weight. The center of the cloud becomes hotter and denser, until eventually nuclear fusion begins and a star is born.