The tool box is a collection of icons arranged vertically in a floating 'panel' that will be displayed for all logged-in user tht have admin privileges on the site. The exact icons displayed will depend on the privileges that have been assigned to that user.
Generally each icon in the vertical stack identifies a functional area of the site, for example content management, email marketing, contact management etc. You can click on any of these icons to visit the control page for that particular functional area.
Most of these top-level icons also open a set of more specific functions if you hover your mouse over the icon. The additional options will be displayed in a separate pull-left (or right) sub-menu. The expanded panel will include icons for specific features and may also include a short-cut dialog providing access to the most common tools. For example the contact management area allows you to directly search for a contact.
You can reposition the panel by dragging it to a new location. The location is saved for the duration of your session or until you move it again.