OOTB stands for Out-of-the-Box. What does Azure Backup has to do with it? Well this blogpost explains how you can protect your VM with Azure Backup at the time of its creation.
Previously when you wanted to add an Azure VM to be protected by Azure Backup, you had to created a recovery services vault and select the desired VM or you had to allow backup through the VM Management blade. The catch here is both these options are post creation activities. In my opinion, administrators often forget to protect their Azure VMs post creation. With this new update, we can protect our Azure VMs during it’s creation.
When you create a VM in the portal under Settings > Configure Optional Features blade you can find the backup option now.
Here you can create a new recovery services vault or select an existing one and then create or choose an existing backup policy to backup your Azure VM.