On Azure, there are usually two order types: BYOL and PAYG.
BYOL offers perpetual (normal series and v-series) and annual subscription (s-series, available starting Q4 2019) licensing as opposed to PAYG, which is an hourly subscription available with marketplace-listed products. BYOL licenses are available for purchase from resellers or your distributors, and prices are listed in the publicly available price list that is updated quarterly. BYOL licensing provides the same ordering practice across all private and public clouds, no matter what the platform is. You must activate a license for the first time you access the instance from the GUI or CLI before you can start using various features.
With a PAYG subscription, the FortiGate-VM becomes available for use immediately after you create the instance. Term-based prices (hourly or annually) are mentioned on the marketplace product page.
In both BYOL and PAYG, cloud vendors charge separately for resource consumption on computing instances, storage, and so on, without the use of software running on top of it (in this case FortiGate).
For BYOL, you typically order a combination of products and services, including support entitlement. New s-series SKUs contain the VM base and service bundle entitlements for easier ordering. PAYG includes support, for which you must contact Fortinet Support with your customer information. See Support Information on the marketplace product page.
To purchase PAYG, all you need to do is subscribe to the product on the marketplace. However, you must contact Fortinet Support with your customer information to obtain support entitlement. See Creating a support account. Also see Support Information on the FortiGate BYOL marketplace product page.
PAYG FortiGate-VM instances do not support the use of VDOMs. If you plan to use VDOMs, deploy BYOL instances instead.