What is after-hours trading, and how does it work?

After-hours trading happens after the market closes, but an investor can buy or sell securities outside the regular trading hours. You can complete trades in the after-hours session through the electronic communication network (ECNs) that matches potential stock buyers and sellers without using the traditional stocks exchange.

Yes. You can buy and sell most stocks on some brokerages during after-hour trading. Wall Street hours are 9.30 - 4.00 ET, but they also allow after-hour trading for 4 hours before they open and 4 hours after they close.

Stocks can move a lot in the after-hours because investors cant trade options contracts which are sometimes used to manipulate and hold stocks during hours.

Yes, stocks only move from Monday to Friday because the stock markets close on weekends.

Also, stock prices tend to converge across exchanges because stock buyers and sellers can place their orders on any exchange. There are also so many stock prices on different exchanges and often different prices over many trades. Therefore, prices tend to become very similar on different exchanges.