Azure resources are the key to every service offering in Azure. Resources are the smallest building blocks and represent a single technical entity, such as a VM, a network interface card, a storage account, a database, or a website. When deploying a web app, a resource called app service will be deployed along with a service plan for billing.

When deploying a virtual machine from an Azure Marketplace template, a VM resource will be created as well as a storage account resource holding the virtual hard disks, a public IP Address resource for initial access to the VM, a network interface card, and a virtual network resource.

Every resource has to be deployed to one specific resource group. A resource group can hold multiple resources, while a single resource can only exist in one resource group. Resource groups also can't contain another resource group, which leads to a single layer of containers regarding resources.

One resource group can contain all resources of a deployment or multiple resources of different deployments. There are no strong recommendations on structuring resource groups, but it's recommended to organize either the resources of one project/enrollment/deployment in separate resource groups or distribute resources based on their purpose (networking, storage, and so on) to resource groups.