What is investing on margin all about?How do you properly set up an onlinetrading account? What's the differencebetween a market order and a limit order?If you are in the dark about any of thesefinancial subjects, a quick run through theeducational online investment simulatorput up by the North American SecuritiesAdministrators Association (www.investingonline.org) can enlighten you. Thesimulator allows you to track hypotheticaltrades and experience profits and lossesfirsthand. You'll learn, for instance,that a market order allows a broker toexecute a trade for you at any price,whereas a limit order must be executed atthe price you specify or not at all. Forvolatile stocks, the simulator suggests, alimit order is the better way to go. There'salso a quick quiz to help you determine ifyou're ready to invest online.