In general the process of taking some convoluted internal data structure and generating a linear representation of it that can be used to reconstruct the internal data structures at a later time. This is the fundament underlying persistence and transfer of complex data over channels.
Great that be doable, better that be done (where worries go).
TV: But in various cases it should be so much simpler... Agreed, though. - RS: This page lists only the nontrivial cases. Other languages will have to worry about how to serialize an integer, a double, a list, an array... which Tcl all provides with built-in string reps, as specially simple case of serialization.
escargo 2004-02-21: This could also be seen as an implementation of the Memento design pattern.