V - model :verification and Validation model.
It is the best model than  the all other old development
and testing models.
Actually V-model is highly improved model for fast  
       application or product development.

           V-model looks like
 

       BRS                      Acceptence Testing
        \                          /
        SRS                    system testing
          \                       /
          HLD                  system integration testing
           \                     /          STLC
 SDLC       LLD                Component Integration Testing
             \                  /
             Coding          Unit testing
                 \            / 
                    Testing 
     

V-model spilts the testing into two parts design and 
development.

Test design is done in early and test execution done at 
end of testing

This enables the testing team to review and improve the 
test cases. 
verification and validation processes will be done 
parallely.
In old conventional waterfall model testing is end cycle 
activity.

Right side part majorly involes in Software development
and Left side part majorly involves in Software Test life 
cycle.

And also one more important thing is right side half of the 
V-model resembles like waterfall model.

As every body knows that waterfall model has no back 
tracking to correct the defect occured in the previous 
phase of the development.The defect resolving task will be 
postponed to next release.

byee friendz,
if you have still any doubt
feel free to contact me by Mail or call
Rajendra Prasad Reddy
rajendra_penumalli@yahoo.com
9885162742
hyderabad