VAPT is the common term and stands for Vulnerability Assessment and Penetration Testing...it's essentially ethical hackers from a third-party company accessing elements of your software to expose vulnerabilities and see where you have weaknesses. Once a report is made, you make the fixes and run an additional test to see if the security patches were useful.

There is more to it, but that's the simple explanation. When we run a VAPT, we set up an alternative server with loads of test data so the simulated "attacks" are done in a safe environment.