A mug is a type of cup typically used for drinking hot drinks, such as coffee, hot chocolate, or tea. Mugs usually have handles and hold a larger amount of fluid than other types of cup. Travel mugs (introduced in the 1980s) generally employ thermal insulation properties for transporting hot or cold liquids. Similar to a vacuum flask, a travel mug is usually well-insulated and completely enclosed to prevent spillage or leaking, but will generally have an opening in the cover through which the contents can be consumed during transportation without spillage. http://www.lancewaterbottle.com/cup-and-mug/travel-mug/