Test strategy is the formulation of the approach to test a product, defining the levels and types of testing required, the techniques to be applied, the extent and kind of test automation required.
Test plan describes what specific tasks must be accomplished and who is responsible for each task, what procedures are to be used, how much time and effort is needed and what resources are essential to carry out the activities of testing. Test plan details out the operational aspects of executing the strategy. Without a plan we don’t know, What to do, How to do, who has to do, How long to do, Where to do, When to do, What does it take to do (resources).