"ERG" in this context is probably an Employee Resource Group - a pretty common construct at larger organizations. Think of them as a formal way for employees with some kind of shared set of goals or concerns to organize and support each other, usually completely distinct from their actual job function.

ERGs often have some kind of liaison from HR, especially since they are often associated with diversity programs. But the ERG itself is usually just advisory if they're consulted on something the company is doing.