The concept is just like SimCity in which you build residential, business and industrial buildings to grow your city but with less dynamic pizzaz of the PC game. Nevertheless, it's still a fun game to play. You get Simoleons from your businesses, which you can upgrade to give out more cash. Your factories produces materials needed to build and upgrade other buildings. Diamonds are handy when you need a faster way of completing the tasks at hand. Residential buildings can accomodate up to 660 people but needs to be supported by attractions that can increase population. You are initially provided a few plots of land. After that, you'll need to buy the adjacent land in order to expand. The more plots you unlock, the more simoleons you will need to expand the next plots.
the tasks you are able to do at a time depends on Energy. It regenerates every 3 minutes. I'm so hooked to this game that I some time waste my time just waiting for energy to regenerate. You can either build your city to your liking or follow the storyline based objectives on the left of the screen. Completing objectives will give you extra simoleons, materials or buildings. As your population increase, more buildings will be unlocked. As it's a social game, having friends that play this game is very crucial (unless you have or buy lots of diamonds). They will help you staff some buildings, provide you with land permits to expand the city and also other items required to activate or upgrade certain buildings. Don't worry if you don't have a lot as the same friends can provide you the same items but only on different days. You can also visit their city to gain some items only available for visiting neighbors.
When I started this game, they had this Olympics theme so you needed to compete in their Olympics and you can gain free items including Diamonds. So I guess that made me played more often than I'm suppose to (Plus I'm currently very free..). Should definitely give it a try.
SimCity Social: http://www.facebook.com/simcitysocial