There has been a bit of a quiet in the past month regarding Paradox Interactive. Fans of games such as Crusader Kings and Stellaris have those games to tide them over until further updates, but those awaiting Victoria 3 eagerly await any news.
If asked to point out the defining trait of Victoria, long-time fans of the series will simply answer: "The pop mechanic". This way of organizing and categorizing the world was a first in grand strategy games, and even though other titles, such as Stellaris have adopted it, none have used it to the same success quite as Victoria did, and it will also deepen in Victoria 3.
The main way of acquiring wealth in Victoria 3, both for countries and the Pops living in them, is via the manufacturing and selling process of Goods. These can be divided into four types, and are consumed by either Pops or Buildings, with no hard lines of differentiation, as nothing is ever set in stone in an everchanging world. These Goods are Staple Goods, Luxury Goods, Industrial Goods, and Military Goods.
One important part of any strategy game are Buildings. Victoria 3 takes a different approach to these than the standard present in most games, with Buildings being heavily dependant on their surroundings. These Buildings, on the other hand, deal with Production Methods. Upgrading them means interfering with the Production process.
While upgrading in Victoria 3 is by no means a bad thing, not only are certain conditions required to be present, but the players must be aware of what exactly those upgrades represent. Perhaps upgrading a factory will put a strain on the market regarding the materials needed, or the workers may go out of jobs if technological advancements are high enough, or the new product is not as well-received as the old one, whose production is now suffering due to a change in Production methods.
And, finally, we have Politics. Politics in Victoria 3 will be handled via Interest groups.
Interest Groups are fundamentally made up of Pops - all individuals in all Pops are either members of an Interest Group or Politically Inactive, with the ratio in each based on factors such as Profession, Wealth, Literacy, and other such categories. Individual Pops contribute strength to their respective Interest Groups, depending on their personal wealth, education, and other socio-economic strength.