In terms of gameplay, FFE is a lot like its predecessor, Frontier, but with improved graphics, most noticeable of which is the 3D planets and terrain. Set 50 years after FE2, there are a number of new ships, new equipment and the return of the dreaded Thargoids, who were sadly (!) missing from FE2 (although rumours persist that there is a solitary Thargoid hiding somewhere in FE2, backed up by the existence of an actual Thargoid-shaped ship which you can fly by hacking the game). There are now five newspapers, which report events in the galaxy in their own styles and from their own viewpoints, and often keep an eye on your actions too.
If you want more information, then have a look at some of the sites on the Links Page.