Macro Buttons are user-clickable buttons that execute a macro with a single click (as opposed to having to type the entire macro to chat). When a macro is created, it automatically generates a labeled button (the label is the name given by the macro author to the macro).
The screenshot below shows some example macro buttons. Note that buttons can have varying button and font colors, and can be sorted and arranged in various ways.
When the macro button is clicked, the contents of the macro are populated to the Chat Panel and the commands are parsed and executed.