In the Market menu there is initially one tab: Trade. At Market Level 30, a second tab is unlocked: Auction House.
In the Trade tab, you have the option of either buying or selling Food. In the upper portion, the current Food Price is shown: This number is the buying/selling price in Gold, for one unit of Food. The Food Price changes between 0.1 and 0.5 once every 30 minutes.
Below the Food Price is the Remaining Trades amount, followed by the maximum number of trades allowed per day. This number lowers each time you make a trade either buying OR selling. It refreshes every 24 hours. The maximum trade amount is raised with each upgrade to the Market.
In the lower portion of the Trade tab, you have two sliders: the upper slider for purchasing Food, and the lower slider for selling Food. to the right of each slider is the button pressed to complete the transaction. Below each button is a small window that shows the amount of gold that is required (buying) or received (selling) for that particular transaction.
Below the sliders is the Black Market button.The Remaining Trades amount can be reset for 2 Diamonds and or Cash Gift. There is a cooldown time after each use of the Black Market.