Apple Logic Pro 9 - Manual (Page 84)

Checkboxes and Buttons
Checkboxes are square boxes that are selected when you click them, in order to activate
an option (or function). Click the checkbox a second time to turn it off, and deactivate
the option.
Some buttons behave in a similar fashion, in that the function they represent is temporarily
enabled (while the button is clicked, and usually illuminated).
A second click on the button disables the function. Examples of these types of buttons
include the Mute and Solo buttons.
A different type of checkbox is the round radio button. A number of grouped buttons
(each representing a different option) are available, and you need to select one of them.
They differ from checkboxes and other button types in that only one of them can be
activated at any given time. A good example are the Type radio buttons in the New Tracks
dialog.
Pull-Down and Pop-Up Menus
Pull-down menus open when you click the menu name. Pop-up menus open when you
click certain input fields or buttons.
In some menus, an arrow is shown beside one or more items, indicating a submenu. To
choose an item from a submenu, move the mouse in the direction of the arrow, and then
move vertically over the desired item. Click to activate the chosen command or setting.
84 Chapter 3 Overview of the Logic Pro Interface