Depending on which difficulty you select you'll start out with a bunch of goods and some people. The harder the difficulty the less goods and citizens you will have. Then you will have to look around the landscape and start planning out your town. Food and firewood, are important resources to start gathering and they will need to be stockpiled for when the harsh winter rolls in. Surviving the winter is one of the biggest challenges of the game and not being prepared for it can kill your towns inhabitants. The game also has disasters like tornadoes and fires, plus infectious diseases can break out amongst your livestock and crops. So yes, survival is the main aim of the game.
Unfortunately Banished is not without its issues. I did encounter a few bugs, the most annoying of which was my cursor disappearing. I also had the bug that only allows you to install it on C: drive though there is a work around for that here. I also had a known bug that causes the game to crash when you are viewing the paths your citizens use. They are fairly minor issues and they are being looked into but as the developer is only a very small company, it may take sometime to resolve all this, which is one thing to consider when purchasing. There isn't a huge amount of content in Banished and the late game suffers a little from this. Sure you can collect every last type of seed and livestock but that isn't as rewarding as having something completely new and different to build. However, the developers will be launching a modkit soon which will hopefully alleviate this problem. The only thing is again you are going to have to wait.
I know a lot of people like me were looking forward to the release of Sim City but were bitterly disappointed with the poor decisions made by Maxis and EA on that title. I think a lot of people who felt that way will really enjoy this game because it has so much more charm and even comes in a DRM free version. For those of you who are big fans of this genre it is a must have right now, for everyone else, it is worth waiting and picking up on sale. Once the modding community has got its hands on the modkit, the major issue of lack of content will disappear and judging by it's current success it may even see an expansion or two. This game is like a fine wine, it needs time to reach its full potential but I really think it will make it there 7.9/10.