This structure, which is placed in your clan dojo (you might have to ask someone in your clan where it is if you can't find it), facilitates trading with any other player that is physically in your dojo. In Warframe, clans are basically player-run guilds that you join to find friends to play with and access all sorts of handy features-one of the them being access to a trading post. You can buy platinum for real money or sell items to make some. Most players prefer to trade their items for platinum (often written as 'p'), Warframe's in-game currency. We'll cover the clan dojo method first since it's the most common way of trading.
Trading in Warframe happens in one of two locations: A clan dojo or Maroo's Bazaar.