Resource group

Resource group is a logical container into which Azure resources (web apps, databases, storage aacounts) are deployed and managed.

Required by all services/resources to be created.
Updating resource requires resource group to be passed (unless resource name is unique).

API: az group create | New-AzResourceGroup

az group create
    --name
    --location

Move to different resource group / subscription:

$res1=$(az resource show -g OldRG -n res1Name --resource-type "<type>" --query id --output tsv)
# res2=... another related resource
az resource move --destination-group NewRG --ids $res1 # res2 res3 ...
# Add `--destination-subscription-id $newSubscription` to change subsription

Microsoft.Web/sites: Web app
Microsoft.Web/serverfarms: App service plan