We identify all possible issues before releasing it into the market or to the user.
In this testing is typically done by end-users they used that product and gives the feedback.
This Tests are based on the requirements and functionality.
In this testing internal coding part like statements, branches, paths, conditions are tested.
In this tesing checkes how much software is secure from the malicious program, viruses.
In this testing check whether the system performance of stress and load.