You create a reference by claiming a video and turning on Content ID matching for the video. References can also be created by uploading spreadsheet templates.
From a reference file, YouTube creates a digital fingerprint that Content ID compares with videos uploaded to YouTube by other users. When Content ID detects a match, it automatically claims the video on your behalf and applies your match policy to it.
FAQ
What’s the difference between a reference and an asset?A reference is one component of an asset. An asset can have more than one reference. For example, a movie asset could have separate references with 16:9 and 4:3 aspect ratios.
An asset is a collection of info about a piece of intellectual property. Assets are made up of references, along with metadata info, asset ownership info, and policies.A reference is the representation of your intellectual property for Content ID matching. You upload a reference file, then Content ID uses that file as a reference when it’s searching for matches of user-uploaded videos.
A video is the representation of your intellectual property on YouTube. The video uses the same media file as a reference.In general, it’s recommended you choose full-length files to use as references, rather than short clips. Full-length references result in more Content ID matches and higher monetization rates.
For more info on choosing effective references, go to Best practices for references.