QA stands Quality Assurance. QA is a set of activities designed to ensure that the developed software meets all the specifications or requirements mentioned in the SRS document.
QA follows the :
The plan is a phase in Quality Assurance in which the organization determines the processes which are required to build a high-quality software product.
Do is a phase of development and testing the processes.
This phase is used for monitoring the processes and verifies whether these processes meet the user requirements or not.
The Act is a phase for implementing the actions required to improve the processes.