Describe who the system's intended users are and why they will use this software, i.e. indicate the stakeholders and their motives.
Describe in general terms what the system aims to do and the main services it offers. Give a link to the system and three links to similar other systems.
Describe in general terms the HCI interaction structure, including the menus or controls the user sees, how they navigate the site (e.g. by tabs), how it identifies users (and any roles), how user feedback is given, any multi-media, and anything else relevant.
Do not get into too much detail at this point - just an overview of the system, with some screenshots (more detail is given in the next section).