Loose Piece (Queen)

Dec.18, 2017 :  This chess tactic occurs when a piece is undefended, as White's Queen is on move 20. It certainly looks safe enough, but I can move my Rook, which is diagonally attacked by the Queen, to different squares, depending on the position, and my Queen will be threatening his. Here, I can capture a piece with my Rook, and although it is now under attack, if White swaps Queens, I can recapture with the Rook, saving it, thus winning a piece. If White decides to move his Queen safely away, then I'll also move my Rook to safety, still maintaining the piece advantage.  

Hopefully y'all understood this, because I tell ya, I ain't explaining it again!