DRM or Digital Rights Management is a system of digital protections that are used to protect the copyright of digital files. DRM Schemes or DRMs are usually used to prevent piracy of digital media such as music, games, and movies.
DRMs are very popular nowadays since they ensure that media that a company/organization produces would only end up in the hands of paying customers. While digital copyright does protect digital content, enforcing copyright laws involve complicated and often lengthy processes of filing a DMCA takedown notice.
It is important to note the Digital Rights Management is a general term and is not referencing a specific method to protect digital media. Some methods include encryption, special metadata, tracking, and watermarks.