What is the use of plan in Automation?

The purpose of the software test plan is to prescribe the scope, approach, resource, and schedule of the testing activities         The following are the important topics, which helps in preparation of Test plan.
             1.High-Level Expectations
             2.People, Places and Things
             3.Inter-Group Responsibilities
             4.Test phases
             5. Testing strategy
             6.Bug Reporting
             7.Metrics and Statistics
             8.Risk analysis.

Test Planning:

    Test plan: The Test Plan describes the tasks, schedules, approach, resources, and tools for integrating and testing the software application
    The Test Plan answers such questions as:
     What is being tested? 
     What are pass/fail criteria?
     When will each test occur?
     What hardware and software environment is required?
     What features must be tested?
     What features will not be tested?
     What are the responsibilities of individuals and organizations involved in the project?
     Identify the various modules and decide which modules/functionalities will be tested. Clearly mention which items are out-of-scope for testing
     List down the priority of testable items (conflict-resolution between the various players is of importance)

The test plan should include:
    Scope of the application being tested
    Approach to be taken (in detail)
    A tentative go live date
    A list of functions and procedures to be tested and their priority
    A list of who is responsible for testing each function and procedure
    Various milestones and timelines
    Details of the resources
    List of all deliverables
    Risk and mitigation
    Specifies roles/responsibilities of the various players: business analysts, technical analysts, development team, testing team, etc