A bug bounty program is an initiative hosted by organizations that offers a platform to security researchers and white hat hackers from across the globe to showcase their skills and discover any security loopholes in their infrastructure. Depending upon the severity level of the bug report and the details presented within the Proof of Concept (POC), they are either rewarded with remuneration or recognition as a token of appreciation.
While a large majority of the bug bounty programs are public, a few are private events and are strictly invite-based. Such programs have strict terms and conditions that the invitees must always abide by.