What it means is that you'll have a commons, events, gfx, history and maps folder amongst other. Game data will be largely exported to .txt's and map data will be a combination of .txt's and .bmp files. It means the map will be divided into provinces, and armies will be abstracted into a single entity that can only move from one province to another province [if this last bit is confusing, contrast eu3/vicky/etc with the Total War series]. You cannot infer -any- gameplay details like "Does it still mean, that armies have to chase one another over the whole kingdom, before one of them is finally dissolved?" If paradox wanted to they could easily program CK2 to have every battle end with the annihalation of the defeated army. If you want to have a general sense of the breath of the clausewitz engine, I suggest playing EU: Rome, EU3 and Vic2. The main thing that being on the clausewitz engine tells you is, imo, that modding the map, events, nations, etc. will be really easy especially to anyone who already has modding experience with the other clausewitz games. Other then that Paradox, as the people who made the clausewitz engine in the first place, are fully capable of changing it to fit in whatever gameplay mechanic they want.