Pennsylvania Maple Syrup comes in Grade A Light, Medium, Dark Amber and also Grade B. Grade B is for cooking, grade A is for the rest. Most people use the grade A medium and dark for the table syrup maple syrup. Most of the difference is the color, but the darker the syrup is, the more maplely taste it has.
Maple Syrup may come in either a plastic jug or a tin (not necessarily the one pictured below).
