To create applications and systems that are easy to use, it is crucial to understand the user and the context in which the app will be used. Understanding the context helps design systems that anticipate use cases at a relevant time of use. The more unobtrusive and transparent the experience is at the time of use, the better the design. This means the user does not have to think about the device he is using, changes in the environment, or changes in context, and can rely on great functionality and ease of use independent of his situation.
Via Nicolas Weil