When you get started with Azure, you want to ensure that your resource groups and resources are tagged. this is great for Management of your Azure Subscriptions/
You can categorise all your resources with tags. You can also view Billing by Tags.
When you add a tag into the Portal (Or programatically) you can add in any tag name as you go. Once created they come up in a list and you can choose from them again.
You can use Azure Policies to try and Enforce some Tagging Logic
Policies allow you to use the built in or custom definitions. the Policies can then be assigned to a Management group, Resource Group or Subscription
Policies are executed when new resources are created. old resources may not be compliant
You can use built in tagging Policies that are already defined within definitions in JSON (Built in)
Or you can add a new definition by adding your own JSON or copying and amending a built in Policy (Custom)
We are going to have a look at some specific examples of how to use Policies for Tagging.