Marshalling in computer science is the process of putting our data into a format that can exist outside a program. The inverse operation is called unmarshalling.

More formally (from Wikipedia):

In computer science, marshalling or marshaling (US spelling) is the process of transforming the memory representation of an object into a data format suitable for storage or transmission, especially between different runtimes. It is typically used when data must be moved between different parts of a computer program or from one program to another.

Marshalling simplifies complex communications, because it allows using composite objects instead of being restricted to primitive objects.

References

• John Arundel, The Power of Go: Tools
• https://en.wikipedia.org/wiki/Marshalling_(computer_science)