The Main Window:
The Toolbar lets you change the current mode for the document.
The Colors section lets change the document's primary and secondary colors. These colors are used for new vectors and for drawing pixels. You can click the two arrows to swap the two colors.
The Options Bar lets you change common settings for the current mode.
The Frame Chooser lets you view your document's frames and select the current frame. You can also add and remove frames.
The Layer table lets you view the current frame's layers and select the current layer. You can also add and remove layers.
The Canvas is where you actually draw your image.
If your document is being transformed, the transforms will appear here.
The Status Bar shows you the size of your image. Click on it to toggle between showing pixels and points. You can also change the current resolution and zoom here.
The Variable view shows your document's variables. You can edit them and add and remove variables here.