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