The main goal of this game is surviving as long as possible with your town and it's villagers, while building and expanding what you can. You start off with a few people in the middle of nowhere. It is up to you to maintain the welfare and stability of your town and villagers. This is done by providing sufficient food, building houses and protecting your villagers from vile monsters. Not fulfilling these commitments will result in the annihilation of your town.
First of all: food. Food can be found by various means. You can harvest fruits to get started. You can also plant wheat and make bread, which is a little more sustainable. Later on, once you've acquired iron, you'll be able to make an oven and hunt animals and prepare their meat. Combining these is the most durable way to sustain your food levels.
Secondly, housing. Your villagers will need their own private quarters to sleep in. Sure, they can sleep on the ground, but that'll leave them more tired and results in having them sleep longer. If you want to exploit your villagers to the best extent, give them a room with a bed!
Lastly, safety. When you start out this isn't a very big issue, but once you've played a couple of hours you'll start getting attacked: sieges will appear and monsters will rush from the forests or the depths looking only to eat your (probably skinny) villagers. You can stop these by building foritications (e.g. a moat/wall around your village) and raising an army.
To raise an army you need armors and weaponry. These can be made out of stone and bone, so even if you don't have iron or better resources yet, you should be fine during the first few sieges. Building up your military power is recquired to advance in the game regardless;a s you will need resources that can only be found deep underground in caves and dungeons, where monsters also reside.
I hope this gives you a basic idea of what Towns is about, be sure to check out their website for more information and tutorials.
Please note: this game is still in (pre-)alpha, therefore still in development. This game will most likely change in the future.
