An extrasolar planet, also called an exoplanet, is a planet that is found outside of our own solar system. It's kind of like finding a new planet in a different neighborhood!
Scientists look for extrasolar planets by using special telescopes that can detect changes in light coming from stars. These changes can suggest that a planet is orbiting around the star, kind of like the way Earth orbits around the Sun.
Extrasolar planets can be really different from the planets in our solar system. Some are much bigger or smaller than Earth, and others are located really far away from their star (known as a "cold" planet) or really close to it (known as a "hot" planet). Scientists are always excited to learn more about these planets because they can teach us a lot about the universe and the different types of planets that can exist.