How can you sell stocks if you do not have any? This is from a lecture of financial market class. The professor discussed the following: you do not have any stocks. But you sell 200 stocks to someone and you get the money, say $200. then if the stocks price goes up, you lose money. I didn't quite understand this part. Please help me, thank you.
"Shorting" is the term used when someone borrows a stock and sells it at the current price to then buy it back later at hopefully a lower price. There are rules about this as noted in the link that begins this answer as there are risks to selling a stock you don't own of course.
If you look up various large companies you may find that there are millions of shares sold short throughout the market as someone does have the shares and they will need to be put back eventually.