Difference between CMM and CMMi

CMM is a reference model of matured practices in a specified discipline for e.g. Systems Engineering CMM,
Software CMM, People CMM, Software Acquisition CMM etc. But they were difficult to integrate as and when needed.
So the CMMi evolved as a more matured set of guidelines and was built combining the best components of individual
Disciplines of CMM (Software CMM, People CMM etc). It can be applied to product manufacturing, People management, Software development etc
The Capability Maturity Model is a baseline of key practices that should be implemented by any entity developing or maintaining a product which is completely or partially software. With the SW-CMM, the emphasis is on the software practices.
Whereas with the CMMI, we can find both software and systems practices. We can imagine that these models would be the outcome of vast consultation of successful projects which would then be documented in a model of what to do to carry out projects with success and to improve continuously, and recommended to the software and systems engineering community