FarmVille puts players in the role of a farmer building their farm from a small property into a large plantation. It plays as a sim game rather than something competitive, and contains gameplay mechanics lightly integrated with the social networking of Facebook. 
Main Gameplay Design Patterns
Players start the game with the smallest farm size available and attempt to acquire wealth and experience. Land can be plowed, seeds planted in plowed land where they will grow in real time, and fully grown crops harvested for coin. All of these actions generate experience which unlocks new construction options for the player.
A variety of other actions are available to the player, including many which are purely aesthetic in nature; examples include trees, buildings, animals and props of various kinds.
Players can view the farms of their "neighbours" who are usually other friends on the Facebook platform who are also playing the game. While on these farms they can assist with maintenance for experience or give items that would normally cost coin to this neighbour. The act of gifting in-game items confers no direct benefit to the player, however it doesn't cost them and they can hope for reciprocity.
Activity occurring in the game world is logged on the players Facebook wall, allowing other players and non-playing Facebook contacts to observe activity on the players farm.
Other Noteworthy Aspects
- Wikipedia entry for FarmVille
- FarmVille review on Sync
- FarmVille usage statistics on Facebook
- Zynga Game Network Inc website