All 25 process areas in CMMI are classified inside four major sections. Process management
This process areas contain the across project tasks related to defining, planning, executing, implementing, monitoring, controlling, measuring, and making better processes.
Project management
Project Management process areas cover the project management activities related to planning, monitoring, and controlling the project.
Engineering
The Engineering process areas were written using general engineering terminology so that any technical discipline involved in the product development process (e.g., software engineering or mechanical engineering) can use them for process improvement.
Support
The Support process areas address processes that are used in the context of performing other processes. In general, the Support process areas address processes that are targeted toward the project and may address processes that apply more generally to the organization. For example, Process and Product Quality Assurance can be used with all the process areas to provide an objective evaluation of the processes and work products described in all the process areas.
Below is the diagrammatic classification and representation of the process areas.

Figure: - 25 Process Area
Below table defines all the abbreviation of the process areas.

Figure: - Abbreviation of all process areas