The tool bar is a line (or lines) of icons at the top of the Emacs window, just below the menu bar. You can click on these icons with the mouse to do various jobs.
The global tool bar contains general commands. Some major modes define their own tool bars to replace it. A few “special” modes that are not designed for ordinary editing remove some items from the global tool bar.
Tool bars work only on a graphical display. The tool bar uses colored XPM icons if Emacs was built with XPM support. Otherwise, the tool bar uses monochrome icons (PBM or XBM format).
You can turn display of tool bars on or off with M-x
tool-bar-mode or by customizing the option