Okay so you know how when you get a toy, sometimes there are extra little parts or accessories you can buy separately to make the toy even cooler? Well, downloadable content (DLC) is kinda like that for video games!
When you play a video game, sometimes the company that made it will release extra things you can download and add to your game. These can be new levels, new characters to play as, new outfits or weapons, or even just little tweaks to the game to make it run better.
Some DLC you have to pay for, like buying the extra parts for your toy. Other times, the DLC might be free, like when the game company wants to say "thank you" to their fans for playing their game a lot.
It's important to remember that DLC isn't always necessary to enjoy a game - it's just an extra fun thing you can get if you want to. Think of it like getting the whipped cream and sprinkles on your ice cream sundae - it's still tasty without them, but they make it even more delicious!