An Enhanced Driver's License is the functional equivalent of a Passport Card. The purpose of both of them is land transport in northern North America (US, as far as Canada, Mexico, the Caribbean) is concerned.
The EDL is a bit cheaper than a plain driver's license + Federal Passport Card, because much of the identity checking parallels what the state is doing anyway to grant you an ID or driver's license (to comply with the Federal RealID rules). Each state needs to work with DHS to be eligible to issue Enhanced DL/ID, and many states do not bother.