Azure Resource group is mandatory for when entered & create any following the below list
- Virtual Machine
- Web App
- SQL Database
- Third Party Service
- Many more
For Example, if you going to deploy your website with SQL Database in the Azure portal. So that you can create two resources like Web App & SQL Database. Each resource can exist in one resource group. You can add or remove a resource to a resource group at any time. You link from any resource to any resources group. A resource can interact with resources in other resources group.
Create Resource Group
My best suggestion always starts Resource Group first, after entered the Azure Portal.
Select Resource Group in Left Slide & Click Add. It will open one more blade.
Enter name of resource group. After valid a name you can select subscription & resource group location. A resource group can contain resources that reside in different region.
After this notification you see all items like below & pin to dashboard
Once resource groups are ready you use create any resource. Example of Web App