I think what was being referred to is the technique of defining a program, not as source code files which are then compiled/run in an interpreter, but as an in-memory VM environment (think REPLs). The memory-based environment can then be saved to a file, similar to making a core dump.

This changes the structure of programs from a file/disk based structure, to the potentially richer structure of the programming environment (e.g. graphs of objects). Although it comes with disadvantages like losing the tool inter-operability of files.