Okay, so you know when you watch TV and you hear the sounds coming from the TV? Well, sometimes those sounds can be split into different parts, kind of like if you break a cookie into smaller pieces.
Multichannel television sound is when the TV sound is split into different parts and played through different speakers.
Think of it like having different flavors of ice cream. You can have one flavor, or you can have different flavors mixed together to create a new taste.
In the case of multichannel television sound, you can have sounds like music, dialogue, and sound effects each playing from a different speaker. This makes it feel like you're watching a movie or TV show in real life because you can hear sounds coming from different places, just like in real life.
So, if you ever hear sounds coming from different speakers when watching TV, it's probably because of multichannel television sound.