You can look that up on the internet it's not really such a hard question. Your ignorance is showing. Don't say that the sun doesn't exist or imply it. That's just stupid. Of course the sun exists. Its origin is from hydrogen. The hydrogen is attracted to other hydrogen atoms by gravity, which causes them to coalesce together getting bigger and bigger until the mass is enough that under its own gravity, it heats up due to friction and eventually it gets so hot that it turns into a plasma. This is a really easy question. This causes nuclear fusion reactions to occur which produces the energy.