Often referred to as simply Pen Testing this is where companies and organisations invite another company to try to hack into their system, find any weaknesses or issues and then report them. It is rare that a company has these specialist skills in-house and in fact an independent team is very much preferred.
A recognised certification in this field is OSCP, which is run by Offensive Security Certifications, Training, Courses and Services. You can also read The Journey to Try Harder: TJNull’s Preparation Guide for PWK/OSCP | NetSec Focus to understand the journey to get the qualification.