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A number of key items are along the edges -- the top, sides, bottom and back. They wrap around the content, so are generally called the wrapper. 

Generally, you will determine as part of the core design, the items that will be in the wrapper, or account for those that are provided by the app or browser framework. 

Scroll, Annunciator Row, Chrome, Notifications, Masthead, Revealable Menu, Fixed Menu, Chyron, Advertising, Back

Examples of how these work...