By definition, an asset is a collection of info about a piece of intellectual property. Copyright owners create assets in YouTube’s Studio Content Manager so they can manage their copyrighted content on YouTube.
For example, a music video is one type of assets, and comprises other assets such us the sound recording and music composition embedded within (cf. next section for more info).
Assets are not YouTube videos. Assets get linked to YouTube videos when they're claimed. Videos uploaded by copyright owners can be claimed or other users’ videos can be claimed when they include content that matches the copyright owner's asset.
An asset is made up of:Reference file
The actual copyrighted content, such as a music video.Metadata
Info about the copyrighted content, such as its title.Ownership info
Info on where you own the rights to the content and how much of the content you own.Policies
Instructions that tell YouTube what to do when matches of your content are found.