Breakup is when people who were in love decide they don't want to be together anymore. It's like when you and your friend decide that you don't want to play together anymore, but it's more serious because when grown-ups break up, they have been together for a long time and they have feelings for each other.
People break up because they may have disagreements, fights or problems that they can't solve, or they may not feel happy or loved anymore. It is hard for both people and they can feel sad, hurt and angry.
Think of breaking a toy that you really like, it makes you feel really upset and you wish that it was just like it was before. That's how adults feel when they break up. They may feel like they have lost something important in their lives and it can take time to feel happy again.
But, like when you and your friend stop playing together, adults can still be friends after a breakup, or they might decide to never see each other again. It's up to them to figure out what will make them feel better.
It's normal for grown-ups to feel sad when they break up, but talking to other people or spending time with family and friends, doing things they like, and focusing on taking care of themselves can make them feel better.