Okay kiddo, do you know what a movie theater is? It's a big room where you can watch lots of different movies all at the same time.
Well, a television multiplex is kind of like a movie theater. But instead of movies, it's a way to watch different TV shows all at the same time.
Here's how it works. You know how your TV has lots of different channels? Well, a television multiplex is like a bunch of channels all put together into one big group.
This lets your TV company show you more than one show at a time on the same channel. They do it by splitting up the channel into little parts, so they can put different TV shows all on the same channel, but at different times.
It's kind of like spinning a wheel with different TV shows on it, and whenever the TV company stops the wheel, that's the show you get to watch. So you might turn on your TV and see one show, and then later on see a completely different show on the same channel!
And that, my little friend, is how a television multiplex works!