The knight is a piece in chess which is represented by a horse's head and neck. The knight is able to jump over pieces and move in an "L" shape on the board. The Knight has a value of 3 pawns, same as the Bishop.
The Knight is represented with the letter N in algebraic notation as K is already reserved for the King which is technically a more important piece than the Knight. The K in Knight is also silent so N is the most logical second choice.
Movement
The knight's movement is very unique, it moves two squares vertically and one square horizontally, or two squares horizontally and one square vertically (in "L" shapes). Due to this movement, the Knight will always alternate between a light and dark square on each move. The knight is also the only piece that is able to jump over pieces, making the pawn and the knight the only two pieces that can move at the very start of the game.
Strategy
Forks
Due to its movement, Knights are very useful for forks as it not able to be attacked by any piece it's forking except for an opposing Knight. It is important to note that the Knight could still be vulnerable to other pieces on the board.
Positioning
The amount of moves that a Knight is able to make is based on it's position on the board. It is able to have a maximum of 8 moves (also called an octopus knight) if it is located in the 16 center pieces of the board and a minimum of 2 moves if it is located in the corner. This is why it is better to develop Knight's to the center of the board to ensure it has optimal positioning.
This concept follows a famous quote by German chess player Siegbert Tarrasch: "A knight on the rim is dim."
Comparison vs Bishop
Although both pieces have a value of 3 points, a Knight is often not as good in an endgame as a Bishop. A Knight is only able to control one part of the board at a time which makes it a hard piece to use when there are Pawns on both sides of the board though this also applies vice-versa: a Knight is stronger in an endgame with Pawns on only one side of the board.
Knights have the advantage of being able to control squares of either color though even this can come as a disadvantage in a rare situation such as a zugzwang. In the diagram on the right you will see a position where if it was White's turn to move, White cannot win. Though it were Black's turn to move, White could win. This tricky position is based on the fact that players are forced to move when it is their turn and that alternation between squares causes a cycle that decides the fate of the game.