On graphical displays, Emacs puts a tool bar at the top of each frame, just below the menu bar. This is a row of buttons with icons which you can click on with the mouse to invoke various commands. Emacs can also optionally display a tool bar at the top of each window (see Window Tool Bar).
The global (default) tool bar contains general commands. Some major
modes define their own tool bars; whenever a buffer with such a major
mode is current, the mode’s tool bar replaces the global tool bar. To
prevent this replacement from happening, customize the variable
tool-bar-always-show-default.
To toggle the use of tool bars, type M-x tool-bar-mode. This
command applies to all frames, including frames yet to be created. To
control the use of tool bars at startup, customize the variable
tool-bar-mode.
When Emacs is compiled with GTK+ support, each tool bar item can
consist of an image, or a text label, or both. By default, Emacs
follows the Gnome desktop’s tool bar style setting; if none is
defined, it displays tool bar items as just images. To impose a
specific tool bar style, customize the variable tool-bar-style.
You can also control the placement of the tool bar for the GTK+ tool
bar with the frame parameter tool-bar-position. See Frame
Parameters in The Emacs Lisp Reference Manual.
NS builds consider the tool bar to be a window decoration, and therefore do not display it when a window is undecorated. See Frame Parameters in The Emacs Lisp Reference Manual. On macOS the tool bar is hidden when the frame is put into fullscreen, but can be displayed by moving the mouse pointer to the top of the screen.
Keyboards often lack one or more of the modifier keys (see Modifier Keys) that Emacs users might want to use, making it difficult or
impossible to input key sequences with these modifiers. For example,
many keyboards lack the Hyper and Super modifiers, and smartphones
usually also lack Ctrl and Alt modifiers. Emacs can optionally display
a tool bar of buttons that can substitute the modifier keys; this
additional tool bar is known as the modifier bar. Clicking a
button within the modifier bar will cause the modifier key shown on the
button to be applied to the next keyboard event that Emacs reads. The
modifier bar is displayed when the global minor mode
modifier-bar-mode is enabled; to do so, type M-x
modifier-bar-mode.