The Suggestion Box is split between two tabs: Letters and SOS.

Suggestions

Paying attention to the Letters gives you an idea of what your Residents are happy about, or not so happy about. If a Resident isn't happy about something, their mood drops and your Governor Approval Rating (GAR) will drop. So making sure you take care of the unhappy suggestions is very important.

SOS

Every now and then you will be called upon to make a decision to settle an issue in your town. Depending on the choices you make to resolve the issue, your GAR will either rise or fall.

Do your best to keep your GAR high to keep your Residents happy and to get the best daily rewards.