Despite what you may have been taught in school, there are only 4 Great Lakes, not 5; Lake Michigan and Lake Huron are not distinct bodies of water, but one massive body of water joined by the Straits of Mackinac.
DirectX is a collection of application program interfaces (API) created by Microsoft that contain a set of commands and functions that allow programmers to much more easily deal with multimedia and video games. By being able to use prewritten functions in Direct3D, a component of DirectX, programmers can create and manage 3D objects with significantly less code.
In fact, the Xbox 360 not only uses the DirectX API, but the name even derives from the DirectX platform. The version on the Xbox is based on a much older version of the API–the newer versions included in Vista, Windows 7, and Windows 8, are much more powerful.