Stars are huge bodies in space that consist of hydrogen and helium. Because hydrogen is constantly burning inside them, they glow very strongly. Some stars have planets orbiting around them. Our Earth is such a planet and our star is called the Sun. While the sun shines very brightly for us, the other stars in space are just small, faint lights in the night sky.
There are so many stars in space that you can't even count them. All the stars except the sun are so far away that we cannot reach them even with our best rockets. That's because it takes eight minutes for light to travel from the sun to the earth. And the star that is closest to us after the sun is called Proxima Centauri. The light needs more than four years to reach us from there. For other stars, this can even be thousands, millions or billions of years.
The science that deals with stars is called astronomy. The name comes from the Greek word for star. Astronomers also use their telescopes to observe other celestial bodies such as planets and comets. There are small telescopes to look through and huge telescopes that do this automatically. Astronomers then try to make sense of all the information.