Nuclear binding energy is the energy required to hold the protons and neutrons together in an atomic nucleus. This energy arises from the strong nuclear force, which is one of the four fundamental forces in nature. A higher binding energy indicates a more stable nucleus, while a lower binding energy suggests that the nucleus is less stable and may undergo radioactive decay. When a nucleus is formed, some mass is converted into energy, according to Albert Einstein's equation, E=mc². This energy is released during nuclear reactions, such as fission and fusion, and is the source of energy in nuclear power plants and atomic bombs.