By definition, an exoplanet simply refers to a planet which orbits a star other than our Sun. This means that many of the trillions of trillions of planets that probably exist classify as exoplanets. One notable exception is rogue planets – planets that don’t orbit stars, instead directly orbiting the galaxies themselves.
Despite there likely being an absolutely huge number of planets in the Universe, we’ve only discovered about 1800 so far. That’s because spotting a planet is a lot harder than spotting a star – they are much smaller and much dimmer. Even the techniques we use to track down new planets like transit photometry and radial velocity work best at finding gas giants like Jupiter, not small rocky planets like Earth. Despite all of these obstacles, we have enjoyed great success when it comes to uncovering our galactic neighbors and, just like in your own neighborhood, some of them are a little peculiar.