Okay kiddo, so imagine you tell me something and I have to think about it for a little bit before I can respond. That little bit of time is called processing delay.
When you talk, your brain sends signals to your mouth to make the sounds. And when you hear something, your ears send signals to your brain so you can understand what's being said.
But sometimes, things can get in the way of these signals. Like if you're talking to someone on the phone and there's a bad connection, it might take longer for them to hear what you're saying. Or if you're playing a game on the computer and it's slow, there might be a delay when you press a button and something actually happens on the screen.
That delay is the processing delay - the time it takes for the signal to go from one place to another. It can happen with lots of things, not just talking or playing games. But it's important to be patient and wait for things to catch up, even if it feels like it's taking forever!