I'm not Peter, but a CDP is the file extension assigned to a content dispatcher's pack. A fuller description of the process is to open the Content Manager, and select the tab at the top which says "my content". When all your content has filtered, select the line, or icon (depending upon which view you're in) assigned to each of the routes you want to copy and right click on it to bring up the context menu. One of the items in the context menu is "save to CDP". This takes the relevant items from the route, and loads them to a special type of file, the Content Dispatcher's Pack, from which you can move the files to another computer, or if you are really satisfied with your work perhaps to the DLS, or a 3rd party site.
By the way, Julie, CDP files are a good way to back up your content, too, and while Peter (and I) recommend flash drives for what you are trying to do in this instance, it might not be a bad idea to back up your routes to archival media--such as an optical disk (CD or DVD)--too.
ns