This means that you can turn on a switch in one game, save the game, then load up another game, and see that the switch is still off.
However, there may be times when you want to turn on a switch in one game and have it turn on for other games as well. In particular, you might want to be able to be able to record the value of this switch during the title screen.
With this plugin, you can specify that certain data will be "synchronized", which means if you change the value in one game, all other save files as well as the title screen will be affected as long as you save the game.
Note that data will only be synchronized during the save process. Simply turning on a switch does not mean it will be turned on everywhere else.