For example, you and a hundred other people each buy 1,000 shares each of GG to hold for the long term. They will not be for sale for a very long time.
Then, along comes a bunch of unknown strangers, with an opinion prediction or guess, that prices will drop. They can borrow your shares and dump them like garbage into the market place, and actually make the price drop, just as if YOU a the hundred others sold out early.