Naked shorting is the now-illegal practice of selling short shares that have not been affirmatively determined to exist.
Ordinarily, traders must first borrow a stock or determine that it can be borrowed before they sell it short.
Due to various loopholes in the rules, and discrepancies between paper and electronic trading systems, naked shorting continues to happen.
Although controversial, some believe naked shorting plays an important and positive market role in price discovery. Yes naked short selling does happen and with the share imbalance with things that were happening in 2015 we don't really know.