Okay kiddo, a corporation counsel is kind of like the lawyer for a big company. Just like people can hire a lawyer to help them with legal stuff, a big company can hire a corporation counsel to help them with legal stuff too.
The corporation counsel will help the company with things like making sure they follow all the rules and laws that apply to them, making contracts (which are like promises that both sides have to keep), and dealing with any legal problems that come up.
Just like how you have a teacher to help you at school, the corporation counsel is there to help the company and make sure everything runs smoothly.