You can clip a balloon or caption to a panel so that the outline of the balloon or caption is cut off at the edge of the panel. This has the result of adjusting the layout of the text within the balloon or caption so that it remains visible within the panel giving a professional comic panel appearance. As you adjust the position of the balloon or caption the text re-lays out to fit the space available.
The panel highlights in orange to indicate that it is acting as a clipping source and the balloon or caption is clipped and the text laid out to fit within the combined outline.
You can have new elements automatically enabled for clipping by checking the "Clip New Non-image Elements to Panels" checkbox in the Preferences or Options. See Preferences for more information.