What is After Hours trading?

After hours trading takes place after the market closes when the investor can buy and sell securities outside of the regular trading hours. Anyone can trade after hours. It is just your broker that must permit you to trade after hours.
After-hours trading starts at 4 p.m. U.S. Eastern Time after the major U.S. stock exchanges close. The after-hours trading session can run as late as 8 p.m., though volume typically thins out much earlier in the session. Trading in the after-hours is conducted through electronic communication networks (ECNs). The volume for a stock may spike on the initial release of the news but most of the time thins out as the session progresses. The amount of volume generally slows significantly by 6 p.m. There is a substantial risk when trading in illiquid stocks after-hours. So, it can be considered as a pretty risky trading style.