I have just had a look at the .ini file that the 'export config bundle' function produces (you can examine it with something like Windows NotePad), and it is a complete set of configs from the Slic3r config directory (on Windows this is {user}/AppData/Roaming Slic3r). It could be used to copy a complete config set from one PC to another, or to backup it up.
Presumably 'load config bundle' would restore the config set.
You can achieve a similer thing by copying the folder {user}AppData/Roaming/Slic3r/ with all of its subdirectories and files. But the the above function would be much more convenient.
Harvey