Okay, imagine you have a favorite TV show that you always watch every week. Friday night is a special night because you get to stay up a bit later and watch it. But have you ever noticed that sometimes your favorite show isn't on Friday night anymore? That's because TV networks sometimes put shows in a slot on Friday night that people don't really watch. This is called the "Friday night death slot."
It's like when you have a really good toy, but some adults say it's not a good toy anymore and give it away to someone else. The same can happen with TV shows on Friday nights. If lots of people aren't watching the show on that night, the TV network might think it's not a good show anymore and cancel it. So even if you really like a show that's in the Friday night death slot, it might not be on for very long because not enough people are watching it.