Although many people never change their toolbars from the default settings, all standard toolbars on the Mac offer six states: icon only, text only, and icon and text, with all three coming in normal and small size. You can change them by choosing View > Customize Toolbar.

But there's a shortcut that makes it easier to check out each variant. Simply Command-click the toolbar lozenge at the upper right of a window, and the toolbar switches to the next view. Click it enough times, and you cycle back to the start.

From Kirk McElhearn