TestCases,DALC & Microsoft Enterprise Library

i do'nt know that is this right palce(forum/thread) for asking these questions....actually i am facing some problem in these words......

1. what is Test Cases, Data Access Layer Classes(DALC) and Enterprise Library?
2. why should we use these thing?
3. whats the use of these thing when we creating a new project?
4 And if "Coding Standerds" is the only moto for these things then what's the use of creating all.... we can do the same in either DALC or Enterprise Library?

Help me.....

Thanx and Regards
Suds

Test Cases is something that I use extensively.

There are the documentated method for testing the code that you have written. The test case should state what, specifically, is being tested, what the expected results of the test were, what the actual results of the test were and who conducted the test.

My customers like to see these test cases and I always include them in the supplied documentation. In addition, showing them to your customer can help as your customer may ask why thus and so wasn't tested.

Test Cases are, IMO, a very important part of the project documentation.