The market acts as a distributor of resources for your citizens. It is the location where citizens can collect items such as food and firewood to bring to their homes. Your citizens no longer have to walk long distances to collect said items, and they will therefore be back to their job much faster, increasing productivity.
The market has a range. Every citizen within this range will prefer to get goods from the market.
The market also has a well. The well is there for aesthetic purposes and it will not help in case of a fire.