Feature.fm supports three different options for publishing a custom domain.
Root Domain
In the example of a URL https://www.yoururl.com/album123, the root domain would be yoururl.com. In using this option, the root domain you submit can be used only for Feature.fm links you create. While you would be creating new links off this domain on Feature.fm, your domain registrar (eg. Google Domains, Squarespace, Wordpress, etc.), would still be responsible for hosting and maintaining it.
Subdomain
In the example of a URL https://music.yoururl.com/album123, the subdomain would be music.yoururl.com. If yoururl.com is used to host other things - like an official website, blog, or store - then creating a unique subdomain dedicated for creating Feature.fm smart links is the best option to use. While you would be creating new links off this subdomain on Feature.fm, your domain registrar (eg. Google Domains, Squarespace, Wordpress, etc.), would still be responsible for hosting and maintaining it.
Fully Managed
This option is only available on the Pro Marketer plan.
In the example of a URL https://www.yoururl.com/album123, yoururl.com would be what you submit for the Fully Managed option. You can create subdomains from within Feature.fm off of a fully managed domain (i.e. artist1.yoururl.com, artist2.yoururl.com, etc.) and individual smart links from that domain and subdomains. With the fully managed option, Feature.fm will be responsible for maintaining the performance of the published domain.