Document window (in the middle) displays the file you’re currently working on. Multiple open documents appear as tabs in the Document window.

Menu bar (at the very top) shows the File, Edit, and other menus that give you access to a variety of commands, adjustments, settings, and panels.

Toolbox (on the left) contains tools for creating and editing artwork. Similar tools are grouped together. You can access them by clicking and holding a tool in the toolbox.

Panels (on the right) include Properties, Pages, and CC Libraries that contain a variety of controls for working with documents. You can find a full list of panels under the Window menu.