It's a turn based strategy game, so you're trying to build cities, produce military units, research new technologies, and many other things. At the higher difficulty levels the AI is already pretty good at doing those things on it's own, but it also gets some large bonuses that enables other civilizations to outpace you by quite a bit unless you really know what you're doing. Even then, getting a bad starting location or researching the wrong technology early in the game often means you lose badly.

I've heard about that game but I've never played it, what's so complicated about it?

riberet19

gaming

Whic is the most difficult video game you have played?

I've played games that aren't meant to be finished, so technically those would be the most difficult! But the most difficult game that I think I've played is the highest difficulty level of Civilization V.