The process of creating a recording is complex and iterative, with many production stages between capturing sound and releasing a finished recording. Every stage in this cycle can lead to new audio creations, be they a new composition, a new guitar track, a new mix, etc. In each of these “studio events”, there are a number of metadata elements that may be important to capture. Who performed which musical work? Who played which instrument? When and where was this performance recorded? Who was the sound engineer? Which recording components (or, in studio parlance: tracks) were used to create a specific mix? And which sections of these recording components have ultimately been used? These pieces of information are valuable for many reasons, such as attributing credits, ensuring that royalties reach the correct people, and facilitating subsequent studio sessions. In addition, providing richer data to retailers for discovery and marketing increases the audience and, thus, the revenue generated.
Some high-level background on RIN is available here whereas the article here provides an overview of the top-level composites employed by the RIN standard to communicate "studio data". Finally, DDEX provides a RIN FAQ here.