1) A test plan is a document which describes the approach to test a system or a software product whereas Test Strategy is a guideline which describes the test design/methods and determines how the testing to be done.
2) Components of test plan includes- Test plan ID, features to be tested, test techniques, pass/ fail, test deliverable, responsibilities whereas test strategy includes objectives and scope, documentation formats, test process, team reporting structure, client communication, etc.
3) Test plan is all about the specification whereas test strategy tells about general approaches.
4) Test plan can be changed whereas test strategy can not.
5) Test plan is planned for a project whereas different test strategy can be used for different section of a test plan.