Test Planning is most important phase of Software testing life cyclewhere all testing strategy is defined. This phase also called as Test Strategy phase. In this phase typically Test Manager (or Test Lead based on company to company) involved to determine the effort and cost estimates for entire project. This phase will be kicked off once the requirement gathering phase is completed & based on the requirement analysis, start preparing the Test Plan. The Result of Test Planning phase will be Test Plan or Test strategy & TestingEffort estimation documents. Once test planning phase is completed the QA team can start with test cases development activity.
