The most feared words on any stock exchange are margin call. A margin call is made when a position is losing money and more money is required by the broker to keep the trade open. If and when a stock ticker moves quickly, there can be people whose borrowing levels literally bankrupt them as things get worse ... fast. Volatility can be either a blessing or a curse, but if you have too much leverage, it can break a trader.
The trading products you can purchase using these platforms can include stocks, commodities, derivatives, bonds etc. which can be traded between the traders on the stock market with intermediates such as investment banks, stock exchanges, brokers and market makers. A communication network is set-up between the various intermediates and the traders, which facilitates proper execution of the whole system.