How vault is created?

[ngaisteve1]

I noticed that when I run azd init, this file config.json is created but it is empty. After running azd up, I can something created in config.json.

{ "infra": { "parameters": { "eventbus_password": "vault://xxx", "myInsightsResource": "vault://xxx", "postgres_password": "vault://xxx" } }, "vault": "xxx" }

May I know which step created the above? I tried to search for the key vault in Azure but unable to find also. But everything works well. Just that I want to find out the value of this key vault in Azure