Test Case : A Set of input values, execution precondition,
expected result and execution post condition developed for a
particular object or test condition. 

Test Suite : A Set of several test cases for a component or
a system under test. Where the postcondition of one test is
often used as the precondition for the next one. 

Test Script : A document specifying a sequence of action for
the execution of test. 
(Test Scripts are mostly used in Automation rather than
Manual, anyway the concept is same for both). 

Test Scenario : Test Scenario is mostly likely a Test Script. 

Test Plan : A document descibing the objective, scope and
approach, resourse and schedule of intended test activities. 
Which includes
- Test Items
- Object to be tested and not to be tested. 
- Risk analysis.
- Resource allocation 
- Who will do each task. 
- Entry and Exit criteria