Assemblies can be static or dynamic.
Static assemblies :
can include .NET Framework types (interfaces and classes), as well as resources for the assembly (bitmaps, JPEG files, resource files, and so on).Staticassemblies are stored on disk in portable executable (PE) files.
Dynamic assemblies :
which are run directly from memory and are not saved to disk before execution. You can save dynamic assemblies to disk after they have executed.