Loot boxes are extras you can buy in some games with real money. What is inside the box is unknown until you open it – it could be a rare item or cool outfit, or it could be an item you already have lots of.
Because you never know what a loot box will contain, some people have spent a lot of money trying to get rare items!
Some countries have banned games from selling loot boxes because they see it as a form of gambling. Gambling is for adults only but loot boxes can be found in games that are suitable for children.