What is the purpose of test plan in your project?

test plan document is prepared by the test lead,it contains the contents like introduction,objectives,test stratergy,scope,test items,program modules user

procedures,features to be tested features not to tested approach,pass or fail criteria,testing process,test deliverables,testing,tasks,responsibilities,resources,schedu

le,environmental requirements,risks & contingencies,change management procedures,plan approvals,etc all these things help a test manager undersatnd the testing he should do &

what he should follow for testing that particular project.