Replica of an East Indiaman of the Dutch East India Company/United East Indies Company (VOC). The Dutch East India Company was the first corporation to be ever actually listed on an official stock exchange. In 1611, the world's first stock exchange (in its modern sense) was launched by the VOC in Amsterdam. In Robert Shiller's own words, the VOC was "the first real important stock" in the history of finance.
Another phenomenon—also from psychology—that works against an objective assessment is group thinking. As social animals, it is not easy to stick to an opinion that differs markedly from that of a majority of the group. An example with which one may be familiar is the reluctance to enter a restaurant that is empty; people generally prefer to have their opinion validated by those of others in the group.
The most common order types: market, limit, and stop (see my guide, Best Order Types for Stock Trading). Market orders buy or sell immediately at the current best market price. Limit orders only buy or sell these shares at, “$xx price or better”. Lastly, stop loss orders are combined with a market or limit to trigger once $xx price hits. For new investors just getting started, I always suggest just sticking with market orders.
In margin buying, the trader borrows money (at interest) to buy a stock and hopes for it to rise. Most industrialized countries have regulations that require that if the borrowing is based on collateral from other stocks the trader owns outright, it can be a maximum of a certain percentage of those other stocks' value. In the United States, the margin requirements have been 50% for many years (that is, if you want to make a $1000 investment, you need to put up $500, and there is often a maintenance margin below the $500).
How much money do I need to start investing in stocks? The amount of money you need to buy an individual stock depends on how expensive the shares are. (Share prices can range from just a few dollars to a few thousand dollars.) If you want mutual funds and have a small budget, an exchange-traded fund (ETF) may be your best bet. Mutual funds often have minimums of $1,000 or more, but ETFs trade like a stock, which means you purchase them for a share price — in some cases, less than $100).
People trading stock will prefer to trade on the most popular exchange since this gives the largest number of potential counter parties (buyers for a seller, sellers for a buyer) and probably the best price. However, there have always been alternatives such as brokers trying to bring parties together to trade outside the exchange. Some third markets that were popular are Instinet, and later Island and Archipelago (the latter two have since been acquired by Nasdaq and NYSE, respectively). One advantage is that this avoids the commissions of the exchange. However, it also has problems such as adverse selection. Financial regulators are probing dark pools.