A tag is defined by the Oxford Dictionary (https://en.oxforddictionaries.com/definition/tag) as the following:
Azure allows the tagging of resource groups and resources with name-value pairs. Tagging helps in the logical organization and categorization of resources. Azure also allows the tagging of 15 name-value pairs for a resource group and its resources. Although a resource group is a container for resources, tagging a resource group does not mean the tagging of its constituent resources. Resource groups and resources should be tagged based on their usage, which will be explained later in this section. Tags work at a subscription level. Azure accepts any name-value pairs, and so it is important for an organization to define both the names and their...
