Shaped Service- The programs that you run on your computer work using something called port addresses. A port address can be used to group programs into certain classes. If a program connects on port 80, we can be pretty sure that the program is used to browse web pages. If a program connects on port 25, we can be pretty sure that program is used to send mail. If you consider what type programs you use everyday, you will realise that it is a fairly small suite and these programs are common to almost all internet users eg web browsers, mail programs and file transfer programs. A shaped service gives higher priority to these types of "common" programs. Since the programs that are prioritised are well defined, bandwidth is easier to manage and the service can be made cheaper. The shaped service should be good enough for almost all internet users.
Unshaped Service- Ports are not prioritized in an unshaped service which implies all programs get the same priority as all others. This service may be useful to you if you are using a program that most people do not use such as a stock trading program or a game that requires quick response times to international servers. Since the programs that require high priority are not defined, more bandwidth needs to be provided so that it appear that all programs are working equally fast. As a result this service is much more expensive