Buy to Cover Limit Order

A Buy to Cover Limit Order is an order used to attempt to cover (close) a currently open short position at a price that is lower than the current market price.
Example: Suppose you currently hold 100 shares of Pfizer (PFE) that you previously Sold Short @ $30 per share. Assume it is currently trading at $25 per share. You would like to exit the trade (cover) and take profit if it reaches $22 or less.
You place a Buy to Cover Limit Order @ $22 on 100 shares of PFE. Now suppose the price trades down to $22. As long as the price remains below $22 per share, your short position would then be closed at the next best available price that is $22 per share or lower, representing a profit of at least $8 per share ($30-$22).

The main benefit of a Buy to Cover Limit Order is that you may be able to exit your short position at a price that is lower than the current market price and you are able to set a minimum amount you're willing to exit at (your limit price). Buy to Cover Limit Orders are great for taking profit on Short positions.
But, if the stock's price reaches your limit price, but then changes direction to the upside before your order is filled, you will not exit the trade. Also, if the price never reaches your limit price, you will still be stuck with your short position.