Toolbars are one of the main ways of interacting with Opus - they let you perform operations on files and launch programs. Some important points to note about Opus toolbars are:

You can turn toolbars on and off using the list in Customize, from the Settings / Toolbars menu, or by right-clicking an empty space on any toolbar to bring up its context menu.

More:

The Default Toolbars
Dynamic Toolbars
Toolbar Sets