What Aerio and No.78 said.

You find out absolutely tonnes about the history of Gran Pulse from the analectics. Why/who built coocon, why gran pulse is called gran pulse, fal-cie motivation. It's a shame it's not worked into the actual gameplay more. People keep crtisising the plot, holes and lack of development, and it's just a lot of it is in the datalog and most of the analectics aren't obtainable till post game.