What files are saved, to where and why is this used.
The running database of a SmartStruxure Lite MPM controller is in the controllers volatile memory (RAM), in order for this data to be preserved during a power failure or reboot this needs to be saved to non volatile memory (Flash)
The save period is for backing up the controller database to flash memory, this can be set to Never, Hourly or Daily. All programming and runtime information is then saved to the controllers flash memory so that it is not lost during a power failure or controller reset.
Stored data includes Controller status, configuration changes, updates such as trended information or setpoint changes, and Lua scripts.
There are several excellent tutorials and videos dealing with setup and configuration of the SmartStruxure Lite controllers on the SmartStruxure Lite documentation site.