The Staff Directory shows your staff organised by department. It is a friendly list for finding out who is on the team, as opposed to the Staff page, which is a manager's table of numbers. You need the View directory permission.
What you see
People are grouped under their department. There is a Rank Ordering option to change how they are sorted within each group. People currently on leave (an approved notice) are marked, so you know who is away.
Newer Directory features
Workspaces with the newer Directory get a faster Directory that loads in one go and searches instantly, plus extra tools. See "Search, filter and export the Directory, and see rank history (newer)".
What the Directory does not show
It deliberately does not show activity numbers, sessions or quotas. Those are on the Staff page and on profiles, and need more permissions.
Opening a profile
Choose a person to see their profile, if your role has Profiles: view.
Tips
If someone is missing, they may not have a role in the workspace yet (see "How do people join my workspace and get their roles?").
Departments are set up by admins under Settings > Permissions (see "Departments: group your team and use them for quotas and policies").
Related articles
Departments: group your team and use them for quotas and policies
The Staff page: finding people with filters, saved views and exports