From the sounds of this post it looks like backgrounds are what themes were in 4th Edition, while themes are more like class features (especially when compared to Essentials subclasses); backgrounds determine what skills and assets you "ought to have", while themes describe how you "do the things you do".
One of the example backgrounds was a soldier, which grants you Endurance, Intimidate, Survival, and a bonus language, though no word on if it is a bonus, unlocks uses of the skill, skills powers, or what. I am curious if there will be ways to boost existing skills or add new ones. I liked the idea of a ranking system, especially if it synchs up with skill powers and opens up other uses of the skill (or makes some applications easier or eliminates some penalties).
Themes on the other hand apparently dole out feats, and only feats. You get one at 1st-level, and more as you level up. The post doesn't specify bonus feats, so it makes me wonder if feats will solely be the purview of themes, and if you get a choice at certain levels like the monk and ranger from 3rd Edition, of if you just get set ones (again, like the monk and ranger in 3rd Edition).
The claim is that by bundling concepts into neat little packages that it should help speed up character creation, though if you don't like it--despite Schwalb's claims of how "evocative and flavorful" they will be--you can just screw the rules and pick your own skills, assets, and feats. Vagueness aside I am glad that they are at least retaining a good chunk of 4th Edition's level of customization, and the idea of being able to play a fighter with a familiar (and no multiclassing required) sounds cool...so long as it works in execution.