The Cosmological Constant is a term introduced by Albert Einstein in 1917 as part of his theory of General Relativity. It represents a constant energy density filling space homogeneously, which can influence the expansion of the universe. Initially, Einstein used it to allow for a static universe, but later referred to it as his "greatest blunder" when the universe was discovered to be expanding. In modern cosmology, the Cosmological Constant is associated with dark energy, a mysterious force driving the accelerated expansion of the universe. Its value is crucial for understanding the universe's fate and structure, impacting theories about the ultimate destiny of cosmic evolution.