There are two basic types of the CMMI which are staged and continuous. Continuous is better known as simple, but both representations are designed to produce the same results. The best feature of the Continuous CMMI is that lets the organization choose an area or different areas by which an improvement is needed the most. CMMI is all about improvement and in the case of the continuous, the improvements are "hand-picked" so to speak.
There are six levels of continuous CMMI. The first one is incomplete wherein the process is either not performed or only half-performed. The second level is performed wherein all specific goals of improvement were done satisfactorily. The third level is "Managed" wherein the specific processes were planned, implemented and controlled. The forth level comes when there is a defined process. Hence the forth level is called "Defined". The fifth level is the "Quantitatively Managed" wherein the processes are defined under controlled conditions using statistical data to validate it. The last level is "Optimizing" is a quantitatively managed process is being "designed into" the existing processes as part the business process improvement desired for the organization.
The continuous CMMI is a very good approach for organizations that only want to improve certain areas in their processes. If the organization has already existing and working business processes, instead of overhauling the entire process they can just pick out processes and improve these to improve in areas where they deem necessary. In conclusion, continuous CMMI works very well until each level is fulfilled.