Imagine you have a big toy store and you sell all kinds of toys. Now, you want to make sure your toy store is successful and for that, you need to know a lot of things. You need to know how to manage your store, how to price your toys, how to order toys, how to hire people, how to market your store, and so on.
Master of Commerce is a degree that teaches you all of these things but for a real store. It's like going to school to become an expert in running a business. You learn everything about how a business works and how to make sure it's successful.
When you do the Master of Commerce degree, you will take classes that will teach you about things like accounting (which is all about money), management (which is all about people), marketing (which is all about selling), and economics (which is all about how the world works).
After you have learned all of these things, you will be able to run a successful business like a boss! It's like having a secret superpower that makes you really good at business.