Binary black holes are systems where two black holes orbit each other due to their mutual gravitational attraction. These pairs can form when two massive stars evolve and collapse into black holes after exhausting their nuclear fuel. As they spiral closer together, they can emit gravitational waves, ripples in spacetime that were first detected by the LIGO observatory in 2015. When binary black holes merge, they create a more massive black hole and release a tremendous amount of energy in the form of gravitational waves. This process helps astronomers study the properties of black holes and the dynamics of the universe, providing insights into the life cycles of stars and the nature of gravity itself.