Okay kiddo, have you ever had a toy that you really love to play with, but sometimes you get bored or frustrated and decide you don't want to play with it anymore? But then a little while later, you see it again and it looks fun so you want to play with it again? That's kind of like an on-again, off-again relationship!
An on-again, off-again relationship is when two grown-ups are dating but sometimes they break up and decide they don't want to be together anymore. But then later they change their minds and decide to get back together again.
It's like a rollercoaster - sometimes things are really good between them and they are really happy, but other times they argue a lot and can't seem to get along. When they break up, it's like getting off the rollercoaster for a little while. But then they miss each other and decide to get back on the rollercoaster again.
Some people think that on-again, off-again relationships aren't very good because they can be kind of confusing and make people feel uncertain. But other people think that sometimes it's better to take a break and then come back together fresh and ready to try again.
Does that make sense, little one?