Do you actively trade stocks? If so, it's important to know what it means to be a "pattern day trader" because there are requirements associated with engaging in pattern day trading. Once you understand the requirements you have to meet, you reduce the risk that your firm will place restrictions on your ability to trade.
A day trade occurs when you buy and sell (or sell and buy) the same security in a margin account on the same day. The rule applies to day trading in any security, including options.
According to FINRA rules, you are considered a pattern day trader if you execute four or more "day trades" within five business days — provided that the number of day trades represents more than 6% of your total trades in the margin account for that same five business day period.
Source Fool.com