Sun is the only reason why we are alive. Humans, animals and every living presence on earth get life energy from the sun. Like every other star in our galaxy sun get its radiation about 4 x 10^26 watts/s, heat and the tremendous amount of light from hydrogen fusion.
This massive fusion happens inside the core of the sun. Where two protons and two neutrons bound together into an identical helium nucleus particle. After that, produced energy and heat can not release immediately. The core is so dense that it takes a million years to reach its surface. The energy released in sun surface is equivalent of 1,820,000,000 the most powerful thermonuclear bomb ever built Tsar Bombas or 9.192×1010 megatons of TNT per second.