The web part is a specialized widget to display a Microsoft Visio diagram in a modern SharePoint page. It is somewhat similar to the classic "Visio Web Access" part in "classic" SharePoint.
In the SharePoint Store: https://appsource.microsoft.com/en/product/office/WA200002491
See the details on the website: https://unmanagedvisio.com/products/diagram-frame-sharepoint-visio-web-part/
You can add webpart as a standard building block:
- File Browser
- Start Page
- Zoom
- Full width and application page mode support
- Support for custom width/height setting
- Support disabling menu items
- Support disabling some interactivity