Adding Classes to your QuickBooks set-up can help you organize information and run reports to provide insight into how well different aspects of your business are performing. Classes give you a different way to quantify data, while keeping your chart of accounts from getting too detailed or complex.

Here is information, straight from Intuit, on setting up Classes:

https://quickbooks.intuit.com/blog/whats-new/how-to-use-class-tracking-in-quickbooks/

We recommend that all business – existing and new – consider utilizing this feature of QuickBooks.