Explanation
Context of use = A combination of users, goals, tasks, resources, and environments.
The purpose of "Analysis: understand and specify the context of use" is to understand and describe who the users are, what they do, what problems they have, and what their needs are, with respect to the planned interactive system. To understand users and their needs, we can observe users performing tasks, interview users and conduct focus groups.
The context of use is described in user group profiles and personas (who are the users), as-is scenarios (how do users currently do tasks), task models (details about what the tasks are) and user journey maps (how users interact with the interactive system and the organisation providing it)