Users within Site Details shows a list of all Client or otherwise invited users for a Site. Your own Agency staff/users will not be visible within this list.
Where can you find this?
From a Site's 'Site Details' page, click on the tab called 'Users'.
How can you filter users?
You can filter by search, or by clicking the column toggles next to 'Name', 'Email Address' and 'Company'.
How can you find out more information about a user?
You can do this by clicking on the name of the user or by clicking the pencil icon on the right hand side of the list of users.
This brings up two tabs:
User Details - Unique user ID; name; email; company; and user level (client or agency)
Sites - All of the sites that this user has access to