So imagine the world is a big puzzle and it's made up of lots of different pieces called continents. There's a place in the southern part of the puzzle called Chile.
Now, Chile is a very special place because it's not just part of one continent, it's actually part of three different continents! Those continents are South America (where Chile is mainly located), Antarctica (the icy place at the bottom of the world), and Oceania (which includes lots of little islands in the Pacific Ocean).
Because Chile is connected to three different continents, people sometimes call it "tricontinental," which is just a fancy way of saying it's part of three different parts of the world.
So, in summary, Chile is a country in South America but it's also part of Antarctica and Oceania, making it "tricontinental."