A JSP renderer is a .jsp file that essentially defines the layout of the content you create. It determines what elements of the content get displayed where. A renderer is independent of the content it serves. For instance, a scenario may call for content from a particular folder of a repository. For one slot it may use Renderer A to display the content, a solution title perhaps, in one line with left alignment. In another slot, or for another panel, the scenario may call the same content, and use Renderer B to display the solution title wrapped on two lines with right alignment. While the content comes from the same repository, its display may be different depending on the renderer.
It is important to note that renderers are specific to one item-type. Recall that offer management currently supports five item types: Solution, Product, Media-text, Media-external URL, and Media-image.