Helium burning is a nuclear fusion process that occurs in stars when they exhaust their hydrogen fuel. During this phase, the core temperature rises significantly, allowing helium nuclei to combine and form heavier elements like carbon and oxygen. This process typically happens in stars that are more massive than the Sun, as they reach higher temperatures and pressures in their cores. As helium burning progresses, it can lead to the creation of new elements through a series of reactions known as the triple-alpha process. This process is crucial for the evolution of stars and contributes to the chemical diversity of the universe, ultimately influencing the formation of planets and life.