Abstract: In the century of the internet revolution and technology innovation that enter in every part of our life, from simple microwave applications used at home to surgeries and critical applications in hospital, hence, came the need to make an assured quality software product and systems. The quality of the software product is depends on the quality of the each phase of the development process used to create it. Verification and validation techniques used across full phases of Software Development Life Cycle (SDLC) to ensure that the phase satisfy its requirement, error free and correctly completed. Verification and validation techniques are set of testing and analysis activities by different methods. This study described first the definitions of verification and validation concepts, followed by verification and validation role in each phase of Software Development Life Cycle (SDLC) and finally the methods of software verification and validation.