The User Interface > Preview/Edit Window
The Preview/Edit Pane is where you can view Clips, and if they're text items, you can edit and reformat them. There are 6 tabs at the bottom of the pane, to display various formats of data (TEXT, Rich Text Format, Bitmap, Picture, HTML, and Binary). Not all will be present – only the ones that are applicable to the data contained within the Clip are displayed.
Aside from being docked into Explorer and Classic, you can also have free-floating editor windows. This can be very helpful if you want to do some heavy-duty editing on a particular clip, or if you want to see the current clipboard contents, but don't want to clutter your screen. To bring one up, click the (optional) "view clip" button or menu option, or press F2 from within either Classic or Explorer.
Here is the editor, shown floating on the desktop. Note the 3 tabs at the bottom, to view the data as Text, Rich Text, or Binary. If it had been a Graphic or Web Page, there would have been other tabs, as well.
By default, the editor embedded within Classic has its toolbar hidden to save space, but you can turn it on. Right-click within the editor box of a text clip, and the option to turn the toolbar on/off is on the menu. You can also do this with "floating" editor windows.