Azure virtual machines are one of several types of on-demand, scalable computing resources that Azure offers. Typically, you choose a virtual machine when you need more control over the computing environment than the other choices offer.
Managed images are helpful in development and test environments where you need a consistent baseline VM. A managed image resource can be created from a generalized virtual machine (VM) that is stored as either a managed disk or an unmanaged disk in a storage account. The image can then be used to create multiple VMs.