Do you know what a stock trader is? Here is a nice explanation.
A stock trader is a person or company involved in trading equity securities. Stock traders may be an agent, hedger, arbitrageur, speculator, or investor. A stock investor is an individual or company who puts money to use by the purchase of equity securities, offering potential profitable returns, as interest, income, or appreciation in value (capital gains). This buy-and-hold long term strategy is passive in nature, as opposed to speculation, which is typically active in nature. Many stock speculators will trade bonds (and possibly other financial assets) as well. Stock speculation is a risky and complex occupation because the direction of the markets are generally unpredictable and lack transparency, also financial regulators are sometimes unable to adequately detect, prevent and remediate irregularities committed by malicious listed companies or other financial market participants. In addition, the financial markets are usually subjected to speculation.
Read more here: http://en.wikipedia.org/wiki/Stock_trader