Here's why:

* They are giant balls of burning gas: Just like our Sun, stars are massive spheres of hydrogen and helium that fuse together, releasing enormous amounts of energy in the form of light and heat.

* They are incredibly far away: The stars we see are so distant that their light takes years, even centuries, to reach us.

* They are vast in number: The universe contains billions and billions of stars, but we only see a tiny fraction of them from Earth.

So, when you look up at the night sky and see a twinkling star, you're witnessing a distant sun burning brightly millions or even billions of light-years away!