Packages are new concept introduced in Microsoft Dynamics 365 for Finance and Operations, Enterprise edition. Package in Finance and Operations is essentially a deployment and compilation unit of one or more models. On the disk a package is a set of folders, consisting of XML files representing the objects. From the compilation and deployment point a package as a whole translates 1:1 as an assembly (DLL). Packages can have references to other packages, just like .NET assemblies can reference each other. One or more packages combine into a deployable package, that is, a unit of deployment.