Hi can any one tell me what is the diffeence between front end and back end testing? Pls tel me with an example

NOTE : [This question was asked by raj, I am posting it in proper forum]

Fron End Testing:
This we can consider almost as black box type testing.
Example:Suppose we are testing yahoo application i.e testing the functionality of login page,inbox,compose and lot many...
Back end Testing:
This we can consider almost as white box type testing.
Like testing the database part..

Front end testing usually has friendly and intuitive user interfaces.A back end testing has its own objects, such as, tables, stored procedures and triggers. Data integrity and protection is critical, Performance and multi-user support are big issues.
To do back end testing, a tester must have strong background in SQL server and SQL language.
Front End Testing is UI testing. and Back end testing is white box testing, that is validation of written code.