Software testing involves executing software components to evaluate properties against requirements. It identifies errors and ensures quality. Benefits include lower costs from early bug detection, improved security, quality, and customer satisfaction. Testing strategies include unit, integration, and system testing. Types are functional, non-functional, and regression/maintenance testing. Methodologies are white-box and black-box testing. The software testing lifecycle has phases for requirements, design, execution, closure, and analysis. Performance testing types include stress, volume, configuration, compatibility, regression, recovery, and usability testing.