The staff tracking feature lets you see which member's of staff are available, when they are due back, and any comments they have left.
It is a panel which can by added to your dashboard from preferences > manage screen layout
From here drag the panel out of the hidden panels section into any of the visible sections. I have placed mine in the bottom visible panels section.
Make sure your users have the corrects tickets so they can view staff tracking and edit it if needed.
To hide users from staff tracking, edit the user from system > users > maintain users, then select the user you want to hide and edit their 'staff tracking' field. The field defaults to 'User Will Appear'. You can set the field to 'User Will Appear' or 'User Will Not Appear' depending on your preference.