Okay kiddo, so you know how sometimes people can speak more than one language? Well, sometimes people can speak three languages and that's called "trilingual".
Now, imagine learning new words in three different languages all at the same time. That might seem really tricky, right? Well, that's kinda what "vocabulario trilingüe" means. It means having a big list of words that you know in three languages.
For example, let's say you know the word "dog" in English, "perro" in Spanish, and "chien" in French. That means you have that word in your "vocabulario trilingüe".
Learning new words in three languages might be tough, but it can also be super helpful because then you can talk to people from different countries and understand them better. Pretty cool, huh?