An action is a stored line of chat text. You can store it by typing the desired text into the chat window and clicking the square-with-a-corner-missing icon to the left of the chat line. This places the action into your toolbar next to the stored coordinates, keywords and frequencies. This is useful for keeping lines of text or commands that you will use more than once. They can be keybound like eveything else by hovering your mouse over the action and pressing a key.