Explanation
These formats are supported in the lists of paths to purge:
Single path purge: Purge individual assets by specifying the full path of the asset (without the protocol and domain), with the file extension, for example, /pictures/strasbourg.png; Wildcard purge: Asterisk (*) may be used as a wildcard. Purge all folders, subfolders, and files under an endpoint with /* in the path or purge all subfolders and files under a specific folder by specifying the folder followed by /*, for example, /pictures/*.
Root domain purge: Purge the root of the endpoint with "/" in the path.
Reference:
https://docs.microsoft.com/en-us/azure/frontdoor/front-door-caching