Galaxy: A galaxy is a massive system bound by gravity containing stars (billions), stellar remnants, gas, dust, and dark matter. Our Milky Way is just one of billions of galaxies in the universe.
Big Bang Theory: The Big Bang Theory is a scientific explanation for the origin and evolution of the universe. It suggests that the universe began as an incredibly hot and dense singularity around 13.8 billion years ago and has been expanding ever since.
Black Hole: A black hole is an extremely dense region in space where gravity is so strong that nothing, not even light, can escape its pull. They are formed from the remnants of massive stars that have undergone gravitational collapse.