Skewering and pinning are essential and favorite moves for many chess players. These are rather basic strategies that often lead to a win. Knowing how to utilize them will help you to improve your game. Your opponent will be forced into situations of either losing their highly valued piece or being placed in check. This gives you the advantage because you are now dictating the game and your opponent is simply trying to survive your advances.
The skewer refers to threatening a highly valued piece such as the queen. Your opponent will likely move that queen and leave a free and open attack to a lesser-valued piece such as a bishop or knight. Picture placing a protected bishop so that it threatens a queen, if that queen moves out of danger the knight is exposed. Your opponent will almost always move that queen, thus allowing you a free victory over the knight. Always take advantage of this. Do not skewer unless you do in fact intend on taking the piece with lesser value.
Pinning refers to threatening a piece that is blocking a file to the king. In other words that piece cannot move, because if it does so the king would be in check and that would be an illegal move. Imagine you have a rook in the same file as your opponent's king, but your opponent has a knight in the file. That knight cannot move because again that would be an illegal move. You are not allowed to place yourself in check. Now you have a choice to take that knight with either your rook or with another piece. Always take advantage of this and capture your opponent's piece. This is a strategy that experienced player's use to successfully win games on a consistent basis.