When using the Azure pricing calculator to estimate the cost of an Azure virtual machine (VM) that will be used for a SQL Server deployment, the "Type" dropdown allows you to select the pricing model that you want to use.
The "OS only" option is used to calculate the cost of an Azure VM that will be used for running an operating system, such as Windows Server or Linux, but does not include the cost of any additional software or services that you may want to run on the VM.
The "SQL Server" option, on the other hand, includes the cost of an Azure VM as well as the cost of a SQL Server license. This option is useful if you want to use the Azure VM as a database server and have the cost of the SQL Server license included in your estimate.
In general, if you are using an Azure VM as a web server, you would choose the "OS only" option. If you are using the Azure VM as a database server and want to include the cost of a SQL Server license in your estimate, you would choose the "SQL Server" option.