Download here :- http://tinyurl.com/nuhso2k
You accumulate resources such as wood, stone and food over time and then spend this building stuff and feeding your population and army.
There is some limited functionality for sending resources to others and therefore trading. Goodgame Studios have also recently introduced outposts, which are like mini castles you can capture and build up from scratch.
Its not all random building though. You receive quests, which are the only way to get experience, and they direct you to build certain building.
Gaining experience means gaining levels. Gaining levels means more types of building and better soldiers to recruit.