The term "young stars" refers to celestial objects that are in their early stages of development and have not yet reached full maturity. These stars are typically less than a few hundred million years old, as they take time to form from clouds of gas and dust through processes such as gravitational collapse or the accretion of material onto an existing star. As they age, these young stars may undergo significant changes in their size, temperature, and brightness, eventually evolving into more mature stars like our Sun.