Pre-market / After-market trading. How many hours? How does it work?

How many hours is Pre-market trading and After-market trading ?

How does Pre-trading and After-trading work ?

What price does apply during Pre-trading and After-trading ?

If I buy something during a Pre-trading or After-trading do I own immediately it ?

Pre-market and after-market let you trade a couple of hours before and after the main market opening time.

Both pre-market and after-marked have some some characteristics like:
- Lower liquidity (because of fewer active buyers and sellers)
- Wider spreads
- Higher volatilty

During pre-market / after-market hours you can buy assets for pre-market / after-market prices.