Test Plan - “A software project test plan is a document that describes the objectives, scope, approach, and focus of a software testing effort”
The purpose of the Master Test Plan, as stated by the IEEE Std 829 is to provide an overall test planning and test management document for multiple levels of test (either within one project or across multiple projects).
You can see the IEEE standard test plan is here.
Test Strategy – Test Strategy or Test Approach is a set of guide lines that describes test design. Test strategy says - How testing is going to be performed? What will be the test architecture?
Test Strategy can be at two levels – Company/Organization Level and Project Level. For e,g, If company is product based, then there can be a general test strategy for testing their software products. Same strategy can be implemented (with/without  some modifications) at project level whenever a new project comes.
  • Test Plan: the set of ideas that guide a test project
  • Test Strategy: the set of ideas that guide test design
  • Test Logistics: the set of ideas that guide the application of resources to fulfill a test strategy