Manual testing is the process of manually testing software for defects by playing the role of an end user and using all features of the application to ensure correct behavior, following a written test plan. The document discusses various concepts in manual testing including software quality assurance, verification, validation, software life cycles, why testing is done, and different testing techniques like black box testing, white box testing, regression testing, unit testing, alpha testing, beta testing, system testing, volume testing, stress testing, and security testing.