As an administrator you're a heavy user with the biggest set of permissions. You can create and manage user accounts and user profiles, and define the permissions for each profile. This is a very important role as permissions define what users can and cannot do in their portal, and that, in turn, has huge impact on data security and the proper use of assets. You're also responsible for the look and feel of the portal and can decide, for example, which image you use to watermark assets.
You can also get various statistical data generated by the portal such as the user and permission change history, or asset upload and download history. You can also monitor who viewed assets.
If you need to train your end-users and what to know what light, regular and heavy users should know, see Train your users.