Historically, SQL Server supported two backup destinations, disk and tape. In SQL Server 2012, a new destination named URL was added. With this destination, SQL Server backs up a database to an Azure Blob Storage container and blob specified in the URL. In SQL Server 2016, Backup to URL was significantly improved, and added support for block blobs in addition to page blobs supported earlier. As customers migrate their SQL Server workloads to Azure IaaS VMs or to Managed Instance, Backup to URL is becoming a very common (and in the case of Managed Instance, the only) way to back up databases.
At the same time, customers are sometimes confused by the differences between the two types of Backup to URL that are available (page blobs and block blobs). The table below describes these differences as a quick summary reference, to help customers choose the right type of Backup to URL for their scenario.