Protostellar development is the process by which a star forms from a cloud of gas and dust in space. This cloud, known as a molecular cloud, collapses under its own gravity, leading to the formation of a dense core called a protostar. As the protostar gathers more material, it heats up and begins to emit energy. During this stage, the protostar is surrounded by a rotating disk of gas and dust, which can eventually form planets and other celestial bodies. The protostar continues to evolve until it reaches a temperature and pressure sufficient for nuclear fusion, marking the transition to a true star.