blackbox  testing is testing the system witout going in the 
inner structure

methods of bbt
eqvilance partioning
error guessing 
boundary value analysis

here black box testing means just giving the i/p and 
checking the o/p wht we r looking for,no need of going 
through the structure of the program..user can do this one

blacking box testing mean's external view of the test object.

Treating the Software as a Black Box, passing inputs and 
checking for resepective response is called Black Box 
Testing. Here the user is not worried about the code or 
structure of the programme.

Checking if ACTUAL RESULT = EXPECTED RESULT.

The process of selecting test cases which are related to
specfication  of the component and not related to internal
structure is known as black box testing. 
diffrent type of bb testing are
1. Boundary value analysis
2. Equivalence partition
3. State transition
4. Decision table

In short, it is Behavioural Testing/Fuctional testing.

Testing the application with out having any knowledge  of 
internal logic.
 
The different techniques which are used for black box 
testing are :
1. Boundary value Analysis.
2. Equivalance partitioning.
3. Decision tables techniques.
4. State transition techniques.
5. Use case based testing techniques.

Black box testing is also known as requirement based 
testing.In this we dont require internal knowledge of the 
application.We are concerned about what it does.We provide 
some input then it gets processed & we observe the 
output.By observing this output we conclude test is passed 
or failed.(By comparing actual result with expected one).

Below are the methods used in BBT.

1) Equivalence Partitioning
2) Boundry value analysis
3) State stansition
4) Decision table.