Okay, imagine you are playing with your toy cars with your friend on a big rug. Now, you want to take turns racing your cars because it's more fun that way, right?
Airplanes have to do the same thing when they take off from the airport. They have to take turns because if they all try to take off at the same time, it would be dangerous and they might crash into each other. That would not be fun.
So, instead of taking off one after another, they use something called a minimum interval takeoff. It means that each airplane waits a little bit of time before taking off after the one in front of it.
Think of it like this: Your friend takes his car and goes first, then you wait a little bit, and when your friend's car is far enough away, you take your turn and go, and then he waits a bit before it's his turn again. The airplanes do the same thing, but it's a lot more complicated because there are many airplanes waiting in line to take off.
The people who control the airplanes make sure that every plane has enough space and time to take off safely, so they use this method to keep everything organized and safe.