Freedom and Liberty! Do whatever you want in a massive open world with hundreds of locations, characters, and quests. Join multiple factions vying for power or go it alone, the choices are all yours.
I checked the page for Fallout 3, to see if they made a similar claim, but they didn't mention anything similar to this. The New Vegas page has a similar quote, it being
Feuding Factions, Colorful Characters and a Host of Hostiles--A war is brewing between rival factions with consequences that will change the lives of all the inhabitants of New Vegas.
It also has another feature listed as
Let it Ride--In a huge, open world with unlimited options you can see the sights, choose sides, or go it alone. Peacemaker or Hard Case, House Rules, or the Wild Card - it's all in how you play the game.
New Vegas obviously had a faction rep system, and the feature for Fallout 4 seems a lot similar to the ones listed above then the feature list for Fallout 3. What do you guys think?