Test Scenario: Test Screnario is the condition or situation 
for which the testing need to be done.
For e.g If we take the example of the ATM machine. The ATM 
m/c has following functions
-Check the balance
-Withdraw of money
-issue of passbook
-mini Statement.

So we can consider each functionality as a scenarion and we 
can follow the basic and alternate flow to write the test 
cases.

Test Suit: keeping same functionality test cases together 
is called as Test Suit. 

Test Case: The action to carried out to test a particular 
functionality is called as test cases. It consists of 
Steps, Description, Expected Result and Actual Result