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.
A barter system is an old method of exchange. Th is system has been used for centuries and long before money was invented. People exchanged services and goods for other services and goods in return. Today, bartering has made a comeback using techniques that are more sophisticated to aid in trading; for instance, the Internet. In ancient times, this system involved people in the same area, however today bartering is global. The value of bartering items can be negotiated with the other party. Bartering doesn't involve money which is one of the advantages. You can buy items by exchanging an item you have but no longer want or need. Generally, trading in this manner is done through Online auctions and swap markets.
Corporate barter focuses on larger transactions, which is different from a traditional, retail oriented barter exchange. Corporate barter exchanges typically use media and advertising as leverage for their larger transactions. It entails the use of a currency unit called a "trade-credit". The trade-credit must not only be known and guaranteed, but also be valued in an amount the media and advertising could have been purchased for had the "client" bought it themselves (contract to eliminate ambiguity and risk).[citation needed]
In recent years, barter has enjoyed a resurgence as a means of countering economic insecurity, unemployment and worker exploitation. The nature of modern-day work, the pervasiveness of the Internet and the rise of social networking have all contributed to its spread. Other examples of alternative economic systems include gift economies, sharing economies and time banks.
I wish I came up with this fantastic idea. SharedEarth is a free site that connects landowners with gardeners and farmers in need of space to grow crops (i.e. starting a home vegetable garden). You can find free access to land in exchange for sharing a little bit of produce with the landowner. In a time of a strong and growing local food movement and concerns about food safety, SharedEarth might just be the most important sharing site of all!

Variable Merchant Gold - Adds more gold to select merchants. Merchants in major cities will no longer have the same amount of gold as their small-town counterparts. There are three levels with increasingly greater difference between the gold amounts for city & small town merchants. Personally, I would recommend leaving the Base Merchant Gold at vanilla values and choosing one of the Variable settings instead. You can stack the Variable settings by selecting multiple options in order to get even greater increases in merchant gold, but I really don't recommend doing this as I haven't balanced the values with this intention.

Even before visiting the Marquesas, I had heard from men who had touched at the group on former voyages some revolting stories in connection with these savages; and fresh in my remembrance was the adventure of the master of the Katherine, who only a few months previous, imprudently venturing into this bay in an armed boat for the purpose of barter, was seized by the natives, carried back a little distance into their valley, and was only saved from a cruel death by the intervention of a young girl, who facilitated his escape by night along the beach to Nukuheva.

While one-to-one bartering is practiced between individuals and businesses on an informal basis, organized barter exchanges have developed to conduct third party bartering which helps overcome some of the limitations of barter. A barter exchange operates as a broker and bank in which each participating member has an account that is debited when purchases are made, and credited when sales are made.
Check online swap markets and online auctions that have a bartering component such as Craigslist.com (check under "For Sale" for the Bartering category), Swapace.com, SwapThing.com, Barterquest.com, U-Exchange.com, Trashbank.com and Ourswaps.com. Check for local bartering clubs. Your local Chamber of Commerce may be able to provide you with information on similar clubs in your area.
As Orlove noted, barter may occur in commercial economies, usually during periods of monetary crisis. During such a crisis, currency may be in short supply, or highly devalued through hyperinflation. In such cases, money ceases to be the universal medium of exchange or standard of value. Money may be in such short supply that it becomes an item of barter itself rather than the means of exchange. Barter may also occur when people cannot afford to keep money (as when hyperinflation quickly devalues it).[15]