Keeping up with the influx of new information on distributed energy resources (DERs) can be daunting. DERs are physical and virtual assets that are deployed across the distribution grid, typically close to load, and usually behind the meter, which can be used individually or in aggregate to provide value to the grid, individual customers, or both. A particular industry interest seems to be centered on DERs — such as solar, storage, energy efficiency, and demand management — that can be aggregated to provide services to the electric grid.