A resource group is a container that holds related resources for an application. The resource group could include all of the resources for an application, or only those resources that are logically grouped together. You can decide how you want to allocate resources to resource groups based on what makes the most sense for your organization.
There are some important factors to consider when defining your resource group:
- All of the resources in your group should share the same lifecycle. You will deploy, update and delete them together. If one resource, such as a database server, needs to exist on a different deployment cycle it should be in another resource group.
- Each resource can only exist in one resource group.
- You can add or remove a resource to a resource group at any time.
- You can move a resource from one resource group to another group.
- A resource group can contain resources that reside in different regions.
- A resource group can be used to scope access control for administrative actions.
- A resource can be linked to a resource in another resource group when the two resources must interact with each other but they do not share the same lifecycle (for example, multiple apps connecting to a database).
Mai Ali's Technical Blog 