Azure, Virtual Machine Classifications
Differences between the virtual machine classifications
Microsoft Azure offers many different types of virtual machines. It is import to select the right size virtual machine for your needs to ensure it has the appropriate capacity and costs. When creating new virtual machines in the Azure Portal or building cost estimates in the Pricing calculator you will need to select what kind of virtual machine class you want. Microsoft uses a letter based system for defining the different classes of computers available.
The following article from Microsoft helps explain the differences between the various classes of virtual machines: