A workload is an independent service or work function, such as a web server, database, or container. It doesn't depend on outside elements to function. Managing your workloads will help you to understand how well your applications are running.
In this video, you'll learn what workloads are, and which ones are compatible with virtual machines.
Workloads define the type of work your Virtual Machine instances will perform. Microsoft supports many VM workloads much like on-premises servers. These include workloads such as Microsoft BizTalk server, Microsoft Dynamics, SharePoint, SQL Server, Exchange, System Center, and of course Windows Server itself to name a few. Windows Server 2003 (with a CSA) and later versions are supported for deployment in Microsoft Azure. However for versions that are earlier than Windows Server 2008 R2, there is no Azure Marketplace support, and customers must provide their own images. In fact, Microsoft does not support operating systems that are past their End of Support without a Custom Support Agreement (CSA).
Workloads also include non-Windows operating systems such as Linux. You may find many Azure-Endorsed Linux distributions such as RedHat, CentOS, Debian, Ubuntu, etc. Not to mention there are many 3rd-party appliances such as Checkpoint and Barracuda firewall images.