There a two types of account groups to which you may wish to add a customer:
Collections Account Groups A collections account group allows you to specify that financial transactions conducted with specific groups of accounts should be completed with a particular payment gateway or combination of payment gateway and merchant account.
Functional Account Groups A functional account group allows you to categorize your customers based on some common element such as geography, product, or channel. Customer Support Representatives can have access to all accounts or only accounts within one or more functional account groups.