A corporate group is like a big family of companies that belong to each other. Imagine you have a family with a mom, a dad, and some kids. Now let's say the dad owns a company and he wants to start another company that will be related to what he already does, like making toys. Instead of starting a whole new family, the dad creates a new company that belongs to the family, like a new sibling for you.
Now, when the dad's first company and the new toy company work together, they can make even better things than they could on their own. They might also share things like money and employees to help them both grow. This is just like how you and your siblings can work together to make a cool fort or a fun game.
The thing that makes a corporate group different from a regular family is that the companies are all run by grown-ups who have to follow special rules and laws to make sure they are fair to everyone. Plus, if the companies do something wrong, they can get in trouble and have to pay big fines. But as long as they follow the rules, they can all be successful together!