This is an Azure Function App https://learn.microsoft.com/en-us/azure/azure-functions/functions-overview?pivots=programming-language-csharp.
This Function App is written to fetch Azure Key Vault Secrets and return them back to the .NET app.
To know how to call this function from .NET Maui app see this repo https://github.com/Jugti-Tech/AzureKeyVault.Maui
The detailed blog post is here https://learndotnetmaui.com/2024/06/06/secure-net-maui-app-with-azure-key-vault/