After-Hours Trading refers to trading outside of traditional trading hours of the major securities and futures exchanges. The traditional hours of trade are from 9:30 a.m. to 4 p.m. Eastern Time.
With the rise of Electronic Communications Networks, or ECNs, individual investors gained access to the after-hours markets. Warning of additional risk  involved in the after-hours period of trade, the Securities and Exchange Commission notes on a page on its website dedicated to the issue of After-Hours Tradingthat while after-hours trading promises greater opportunities and convenience for individual investors, the after-hours market can be much more volatile and far less liquid.
- Trading Stocks After Hours is Risky. About.com.