Sisu terminal systems are like special computers that help people communicate with each other when they're very far away. Imagine you have a toy telephone and your friend has one too, but you're standing really far apart. You can still talk to your friend by holding your toy phone up and speaking into it. But sometimes, when you're really far away, your voice might not be loud enough to reach your friend's toy phone. That's where the sisu terminal system comes in.
The sisu terminal system is like a bigger, more powerful toy telephone that adults use instead. When people need to talk to each other from far away, they use these special computers to send their voices through satellites up in the sky. These satellites are like giant mirrors that bounce the voices back down to Earth and send them to the right place.
So if you were on one side of the world and your friend was on the other side, you could use a sisu terminal system to talk to them like you were standing right next to each other. It's like magic!