Trade in Skyrim is oversimplified and uninteresting. A particular type of merchant always has the same amount of gold and offers you the exact same prices as the same type of merchant in another part of the country. Merchants in small towns differ very little from those in the larger cities, and the only factors that affect price are your speech skill and any barter enchantments you might have.
While some people may balk at an online community for finding babysitters, I know several parents who say it’s actually very difficult to find a sitter they can trust. BabysitterExchange started in 2000 as a babysitting co-op, and it has since expanded to the point that members use it to reserve time when they just have some errands run, need help tutoring their kids, or want a temporary house-sitter.
The barter system is a type of trade that involves the exchange of goods and services without the use of money as a medium of exchange. Trade, on the other hand, is a broader concept that includes not just the barter system, but also, international trade, commodities trading, currency trading, etc. The main difference between barter and trade is that while barter trade does not involve money, other forms of trade occur with currency used as a medium of exchange. An important point to note is that the invention of trade whether barter or otherwise has developed a useful system under which individuals, businesses and nations can exchange or sell off the products or goods held in excess and purchase or obtain desired products, goods and services. The invention of currency has greatly simplified this process making trade convenient and fair.

mid-15c., apparently from Old French barater "to barter, cheat, deceive, haggle" (also, "to have sexual intercourse"), 12c., of uncertain origin, perhaps from a Celtic language (cf. Irish brath "treachery"). Connection between "trading" and "cheating" exists in several languages. Related: Bartered; bartering. The noun is first recorded 1590s, from the verb. 

He would have heard of channels and sandbanks, of natural features of the land useful for sea-marks, of villages and tribes and modes of barter and precautions to take: with the instructive tales about native chiefs dyed more or less blue, whose character for greediness, ferocity, or amiability must have been expounded to him with that capacity for vivid language which seems joined naturally to the shadiness of moral character and recklessness of disposition.