This type of code (x15-xxxxx) often appears in the file names of official Microsoft MSDN or Volume Licensing ISO images. It does not refer to a "feature" itself, but to a specific release version of a Windows edition (like Windows 10 Home, version 20H2, 21H1, etc.).
The identifier refers to a specific version of a Microsoft Windows Certificate of Authenticity (COA) label or product key package, typically associated with Windows 10 Home windows home x15 53886 new