The order board allows you to trade items you produce for coins and experience points.

 

To start trading, tap the board and then select an order from the map. To the right of the map, you will see a list of items required to fulfill the order. Tap the Send button under the list to complete the trade.

 

You can also skip an order by tapping this button:

 

Completing multiple orders will grant you rewards such as energy, coins, sets of tools, and growth elixirs. Your progress towards the next reward is represented by the bar at the bottom of the map. 

 

After filling the gauge at the bottom of the order board window, you will get a special gold order. These orders require more items to complete, but also give you greater rewards, including florins and sets of tools.