The systems by which stocks are traded have also evolved, the second half of the twentieth century having seen the advent of electronic communication networks (ECNs). These are essentially large proprietary computer networks on which brokers can list a certain amount of securities to sell at a certain price (the asking price or "ask") or offer to buy a certain amount of securities at a certain price (the "bid").

Price volatility and average day range are critical to a day trader. A security must have sufficient price movement for a day trader to achieve a profit. Volume and liquidity are also crucial because entering and exiting trades quickly is vital to capturing small profits per trade. Securities with a small daily range or light daily volume would not be of interest to a day trader.
The first 9 successful trades produce $900 in profit. On the 10th trade, when the position is down $50, instead of except the loss the untrained trader purchases more shares at a lower price to reduce his cost basis. Once he is down $100, he continues to hold and is unsure of whether to hold or sell. The trader finally takes the loss when he is down $1,000.
You're probably looking for deals and low prices, but stay away from penny stocks. These stocks are often illiquid, and chances of hitting a jackpot are often bleak. Many stocks trading under $5 a share become de-listed from major stock exchanges and are only tradable over-the-counter (OTC). Unless you see a real opportunity and have done your research, stay clear of these.