A file extension is the characters after the last dot in a file name. For example, in the file name winmail.dat, the file extension is dat. It helps Windows select the right program to open the file.
Margin is borrowing money from your broker to buy a stock and using your investment as collateral. Investors generally use margin to increase their purchasing power so that they can own more stock without fully paying for it.But margin exposes investors to the potential for higher losses.ut if you bought the stock on margin  paying $25 in cash and borrowing $25 from your broker  you'll earn a 100 percent return on the money you invested. Of course, you'll still owe your firm $25 plus interest.
If the stock you short increases then your margin levels will fall. When your margin levels fall below 30% your broker will have no choice but to issue a margin call. This forces you to deposit more money into your account until your margin level is brought back up to 50%.. A Margin Trading Account is Need. In order to short sell you have to trade with margin, which on the other hand is not required when buying penny stocks. Whether you like it or not, when trading with margin you are borrowing money from your stock broker.