A macro is a grouping of slash commands assigned to a single button.
To create a macro, type /macros or click on the interfaces button at the bottom left and select Macros. Click on the New button at the bottom. Type in a name for the macro in the Name window at the top. The radio button underneath allows for applying this new macro to all characters on the account. To select an icon for the macro, right-click the box to the left of the name field and select the desired icon. Click Ok. The large text box underneath the name and icon is where the slash commands are entered. Once all the settings have been configured, click Ok. In the main macro window, drag the new icon to the secondary action bar for quick access.