Have you ever played a game where one person gives something to another person, and then the second person does something with that thing? That's kind of like how secundative language works.
In secundative languages, when someone does something with something else, they often get their own special word to show that they are doing that action to something else.
For example, in English, we might say "I gave the ball to you." But in a secundative language, we might use a word like "give" to mean "give to" and a different word like "receive" to mean "get from". So we might say "I gave the ball you-to" instead.
This might seem like a small difference, but it can change the way we think about actions and who is doing what to whom. It's also a really interesting way that different languages can be different from each other.