Well, it's an interesting question. Imagine a star that is 13B years old. Basically it means, the light from the star has been traveling for 13B years to reach

Well, it's an interesting question. Imagine a star that is 13B years old. Basically it means, the light from the star has been traveling for 13B years to reach us. You might say, then the star must be 13B light years away but that's not correct. The thing is we cannot see such a star in visible light spectrum anymore. The light of the star has shifted to infrared or microwave. Why? Because while the light was traveling in spacetime, the spacetime itself expanded and stretched the light wavelength. When you take a redshift into account, you can correct the distance and figure out that the star must be, say, 40B light years away. By the way, note that this is all about the observable universe. There might be stars beyond our observation horizon that we might never see due to rapid expansion of the universe.