The resources gathered from the activated city cards will allow the players to acquire cards from a common pool, allowing them to get improved buildings, technologies, wonders, etc. and therefore to leverage their civilization deck to new heights through more and more efficient card combos. As the common pool of cards progresses (either as players have acquired cards or because they didn't - which leads to one card from the pool to be discarded per turn), the game progresses through eras. Medieval cards are better than classical cards, and industrial cards are even better, but of course those cards are more and more expensive to acquire.
A modular board, at the center of the table, holds each civilization's army. The board is made of Provinces to be conquered. Unoccupied Province's inhabitants are barbarians who will provide resources to the player who defeats them. Holding a conquered province also brings victory points.
The player with the most impressive civilization at the end of the game will be remembered for all time (and they also win the game!).