Premium simply means real Chocolate containing all three cocoa ingredients: Cocoa Powder (solids) Cocoa butter and cocoa liquor. There are many wonderful brands: Merckens, Callebaut, Peters. Premium chocolate MUST BE tempered and will never contain a tropical oil in place of cocoa butter. Premium chocolate or REAL chocolate will note the cocoa content on the wrapper. Chocolate Chips, compound or Wiltons Meltaways are NOT real chocolate. Bakers chocolate is real chocolate but contains little or no sugar or milk products. It is processed quickly so does not have the smooth mouth feel of premium chocolate. Check out this link for a somplete explaination of grades of chocolate and how to select the right one for your project/recipe.
http://gourmetcandymaker.com/select-the-best-chocolate/
BTW you can buy Merckens chocolate through Amazon.com Look for flavors: Yucatan for Dark and Marquis for milk.