Trade is the negotiation and exchange of goods and services for money or for desired goods and services that are possessed by another. Trade, on the other hand, is a broader term which includes barter system, purchase of goods using money, international trade between countries, commodities trading, currency trading, stocks and bonds trading, etc. When the world developed, the concept of currency and money as a medium of exchange trade between parties became a simple exercise as a fixed and fair price was determined for each product or service. Nowadays trade is conducted in many platforms including international trade which is the trade of goods and services among countries through the payment of international currencies such as the USD, GBP, JPY, etc. However, this involves exchange rate risk which can be quite costly. Trading also occurs on share markets wh ere investors buy and sell securities. Commodities traders and currency traders also trade commodities and currencies with the aim of making profits.

When you load the menu option, the values you see displayed will be the values currently in use by your game. Vanilla values are 3.3 and 2.0. If the menu is displaying different values, then you have a mod installed which is already adjusting these two settings. If you choose to select a new setting, Trade & Barter will override the settings from the other mod. If at any time you wish to revert the settings back to those made by another mod, simply deselect this setting and reload your game. You will need to reload your game before the changes from Trade & Barter are fully canceled out.
In a small economy where individuals specialize in trades, they may find the process of setting up a centralized currency and maintaining it an unnecessary burden in order to trade. One option may be to use a commodity to exchange value between parties that want to trade goods or services and this is why gold and silver have been useful forms of currency in many cultures and times. Another option may be to use a barter system to trade.
PaperBack Swap is exactly what it sounds like: a place to swap paperback books. Currently, more than half a billion books are available for trade on the site. Just list the books you don’t want anymore and other members will find them. When someone requests one of your books, you just mail it out and then choose any available book that you want to receive. Swapping is easy, and membership is free. 

There are several disadvantages of the barter economy. Firstly, there has to be double coincidence of wants for exchange to take place. Again the problem of indivisibility of commodities comes in the matter of exchange. Basically such disadvantages and many more called for the emergence of money. Money is used as a common medium of exchange and store of value.
Identify your resources. What items do you have that you could easily part with? Use a critical eye to go through your home, and consider possessions you may have in storage or that another family member or friend is currently using. If you would prefer to offer services, honestly assess what you could provide for others that they would otherwise pay a professional to do. It could be a skill or a talent or hobby such as photography.