The FG system is the first option out of "Curtain Wall System". The main feature of the FG System is to create the buildings' exterior with full of glass. The glasses are set in a recess on the frames and all the gaps between panes are sealed up with special silicon, hence it is a system that you also see glass panes on the exterior side of the buildings.
The PG system is the second of "Curtain Wall System". It is a very similar system in comparison to the Flush Glazing System. The only difference is that the aluminium frames holding the glasses are exposed and visible on the exterior side of the buildings.