The Software Testing Life Cycle (STLC) is an integral part of the software development process, aiming to identify and rectify defects to ensure high-quality products. It is an iterative, cyclical process that includes phases such as requirement analysis, test planning, test case designing and development, test environment setup, test execution, and test cycle closure. STLC ensures that software meets specified requirements and is free from errors by conducting multiple tests across different phases, including usability, regression, exploratory, and sanity testing. Various methodologies like the Waterfall Model, V-Model, Spiral Model, and Agile Model guide the testing process, each with distinct strengths and suited for different project types. The STLC prioritizes early defect detection, thus improving product quality and reducing test cycle time. It is distinguished from the Software Development Life Cycle (SDLC) by its focus on testing rather than development, beginning after the SDLC phases are completed. Adopting best practices in the STLC allows organizations to efficiently address defects, optimize resource use, and enhance the overall quality of software products.