Penetration testing is the method to test and judge the security of a website, the process of hacking and penetration testing is more or less the same. But the intention is different from each other, while hacking your intention is to harm and while conducting penetration testing you want to test the security so that you will be able to enhance it.
Anyways Kali Linux is the point of consideration and how you use Kali Linux to hack a website so that you will know the vulnerability of the project (website).
Here is an interesting video tutorial based on SQL-injection and the overall operation had been performed on Kali Linux.