C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
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Section 36:
36.1 What's this "serialization" thing all about?
36.2 How do I select the best serialization technique?
36.3 How do I decide whether to serialize to human-readable ("text") or non-human-readable ("binary") format?
36.4 How do I serialize/unserialize simple types like numbers, characters, strings, etc.?
36.5 How exactly do I read/write simple types in human-readable ("text") format?
36.6 How exactly do I read/write simple types in non-human-readable ("binary") format?
36.7 How do I serialize objects that aren't part of an inheritance hierarchy and that don't contain pointers to other objects?
36.8 How do I serialize objects that are part of an inheritance hierarchy and that don't contain pointers to other objects?
36.9 How do I serialize objects that contain pointers to other objects, but those pointers form a tree with no cycles and no joins?
36.10 How do I serialize objects that contain pointers to other objects, but those pointers form a tree with no cycles and only "trivial" joins?
36.11 How do I serialize objects that contain pointers to other objects, and those pointers form a graph that might have cycles or non-trivial joins?
36.12 Are there any caveats when serializing / unserializing objects?
36.13 What's all this about graphs, trees, nodes, cycles, joins, and joins at the leaves vs. internal nodes?
[36.1] What's this "serialization" thing all about?

It lets you take an object or group of objects, put them on a disk or send them through a wire or wireless transport mechanism, then later, perhaps on another computer, reverse the process: resurrect the original object(s). The basic mechanisms are to flatten object(s) into a one-dimensional stream of bits, and to turn that stream of bits back into the original object(s).

Like the Transporter on Star Trek, it's all about taking something complicated and turning it into a flat sequence of 1s and 0s, then taking that sequence of 1s and 0s (possibly at another place, possibly at another time) and reconstructing the original complicated "something."