Could someone please explain to me what an un/managed DLL is? And what is un/managed code?
You will get a fair idea on managed and unmanaged code in following article -
Unmanged code will be compiled to machine language to run directly on the hardware.
Managed code will be compiled to a virtual machine called CLR (Common Language Runtime), and compiled to machine language on start by the JIT (Just in time compiler). THE CLR can be compared to the java virtual machine, it is the same concept.
Short answer: Code compiled without .NET framework (plain old DLL).
When you code with .net you get some memory management, garbage collection etc, so it is called managed code. Older versions are unmanaged (for the memory is managed by the programmer)
And to keep things easy, calling from managed code to unmanaged code can be a trye pain.
来源：https://stackoverflow.com/questions/3814467/what-is-an-un-managed-dll-what-is-un-managed-code