The Star Lifecycle describes the various stages a star undergoes from its formation to its eventual demise. It begins with a cloud of gas and dust, known as a nebula, which collapses under gravity to form a protostar. As the protostar heats up, nuclear fusion ignites, leading to the main sequence phase where the star spends most of its life. Eventually, the star exhausts its nuclear fuel, leading to its transformation into a red giant or supergiant, depending on its mass. The final stages can result in a supernova explosion or the formation of a white dwarf, neutron star, or black hole, marking the end of the star's lifecycle.