Imagine a big group of friends and each one of them speaks a different language. They all want to talk to each other and understand what everyone is saying. This is like the European Union, which is a group of many different countries in Europe that all have their own language.
To make things easier, the European Union decided that they needed to have some common languages that everyone could understand. These are called "official languages" and there are currently 24 of them! Some examples include English, French, Spanish, German, and Italian.
These official languages are used in important meetings and documents that involve more than one country. That way, all the countries can understand and participate.
But this doesn't mean that everyone in the European Union can speak all of these languages! Most people usually speak their own country's language, but they also learn one or more of the other official languages in school.
Overall, having these official languages helps the European Union to work better together and be more united.