Generally speaking, a London Fog is a latte made by steeping an earl grey tea bag in some water then adding some sweetness, vanilla and steamed frothy milk. The way they're made from place to place might slightly differ but the overall idea is the same. A london fog from starbucks has some lavender notes throughout which is what makes it different from other london fogs. They also use vanilla syrup instead of a combination of sweetener and vanilla extract, however, the taste is generally the same.