Stars are massive celestial bodies made primarily of hydrogen and helium that produce light and heat through nuclear fusion. They are the building blocks of galaxies and play a crucial role in the universe's structure and evolution. Our Sun is a typical example of a star, providing the necessary energy for life on Earth. Stars come in various sizes and colors, ranging from small red dwarfs to massive blue giants. They are born in nebulae, where gas and dust collapse under gravity, and they eventually die in spectacular events like supernovae, leaving behind remnants such as neutron stars or black holes.