Marshalling

[C# Programming]

Hi all, i asking about marshalling, what it is means, and why we need it???

I face this statment at some code, but i don't know exactly what it means ..;

< // Marshal pointer into a struct
PcapUnmanagedStructures.pcap_if pcap_if_unmanaged =
(PcapUnmanagedStructures.pcap_if)Marshal.PtrToStructure(nextDevPtr,
typeof(PcapUnmanagedStructures.pcap_if));
>