Two squares in a straight line, then one square at right angles. Say it as you play it and you will never mis-move a knight again: two along, one across. From e4 the L takes it to c3, c5, d2, d6, f2, f6, g3 or g5.
h 1 Now look at the same piece in the corner.
a h 1 Eight squares against two. No other piece loses that much by being badly placed, and it is the whole content of the old advice that a knight on the rim is dim. The average across all sixty-four squares is 5.25 squares of attack, against 8.75 for a bishop, so a knight standing on c3 or f6 is already doing better than average and a knight on h3 is not.
It jumps, and nothing else does
Set up the starting position and play 1.Nf3. The knight has pawns on f2, g2 and h2 beside it, a bishop on f1 and a rook on h1, and it lands on f3 anyway.
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d e f g h 1 Whatever stands between the start and the end of the L is irrelevant, friendly or enemy. Only the destination square matters, and the usual rule applies there: your own piece, no; an enemy piece, take it. That is the only exception to the no-jumping rule in the whole game, and it is why knights are the pieces you keep in a position with locked pawn chains, where a bishop can spend twenty moves staring at the back of a pawn.
Every move changes colour, and that has consequences
Look at the first diagram again. The knight stands on e4, a light square, and all eight of its squares are dark. That is always true, because the L changes the file by one and the rank by two, or the other way, and either way the colour flips.
Two practical things follow. If your knight is on d4, a dark square, and the enemy queen is on f6, also dark, she is safe from it this move no matter how close she looks. And a knight is slow: getting from a1 to h8 takes six moves, and even reaching b2, the square diagonally next door, takes four. The knight is a short-range piece with a long-range trick.
The colour rule also gives you a free calculation shortcut. If the square you want is the opposite colour to the one your knight stands on, the trip takes an odd number of hops; if it is the same colour, an even number. From c3 a knight reaches d5 in one move and c5 in two, and no route ever changes that parity. When you are working out whether a knight can get to f5 in time, count the colour first and you will save yourself half the calculation.
The fork is why beginners should love it
Because it moves unlike anything else, a knight attacks pieces that cannot attack it back. A queen a knight’s move away is not attacking the knight at all, while the knight is very much attacking her. And when it hits two things at once, one of them usually falls off.
8 7 2 f g King and queen at once is called a royal fork or a family fork, and it wins the game on the spot. Knights fork more often than any other piece, and it is the first tactic I teach: see the fork puzzles and the beginner guide to chess tactics. The same geometry gives the prettiest mate in chess, smothered mate, where a knight mates a king boxed in by its own pieces because nothing can block a knight check.
Where to put one
On a square in or near the centre, ideally protected by a pawn and out of reach of enemy pawns. That kind of square has a name, an outpost, and a knight on one can be worth more than a rook. A knight on e5 defended by a pawn on d4 attacks c4, c6, d3, d7, f3, f7, g4 and g6: it sits in the middle of the opponent’s position and cannot be chased away by a pawn.
In the opening the old advice is knights before bishops, and the reason is practical rather than mystical. You know where a knight belongs before you know where a bishop belongs. Nf3 and Nc3 for White, Nf6 and Nc6 for Black, are right in almost every opening there is, while whether your dark-squared bishop wants e3, g5, b2 or f4 depends entirely on what your opponent has done.
Two more things about knights that come up. They are worth about three pawns, the same as a bishop, and which of the two you want depends entirely on whether the position is open or closed. And two knights cannot force mate against a lone king, which is one of the odder facts in the endgame and worth knowing before you trade your last pawn for one.