Multi-party authorization is like you and your friends playing a game together. Before you can do something like start the game or make a rule, you have to ask your friends if they are okay with it too.
In the same way, multi-party authorization is when more than one person has to give permission before something can happen. It's like if you want to buy something really expensive, you need to ask not just your mom, but also your dad if it's okay to spend that much money.
This is used in important things like bank accounts, where more than one person needs to approve a big purchase or a large withdrawal. This way, everyone has to agree that it's a good idea and nobody can do something silly or dangerous with the money without everyone being on board.
Multi-party authorization is a way to make sure everyone is involved and has a say in what happens, so that everyone feels safe and comfortable with the decisions that are made.