On the default theme, Opencart only displays the name of a customer group when a customer group option is shown on the customer registration page (more than one customer group setup and configured for that store). This customer group name is restricted to 32 characters. What this mod does is also shows the customer group description field after the name on the customer registration page which allows you to put a more detailed description for your customer, such as

"Please select this default option unless you have been specifically advised otherwise, there is no approval required and you will be able to immediately proceed with your purchase."
"This option is strictly for trade customers and will require approval before use"
etc.

UPDATE 1.01 remove default theme restriction