In the early days of chess, players didn't know what to do with their pawns - they considered them a nuisance to be got out of the way, so that the more powerful pieces could join the fray. Many beginners and novices make the same mistake - they consider pawns worthless and aren't too bothered if they lose a pawn here or there. Make sure you don't fall into the same way of thinking.
The first player to really recognise the power of pawns was the 18th century master Philidor, who called pawns "the soul of chess". Nowadays, chess masters understand that pawns and pawn formations - known as pawn structure - are the cornerstone of chess strategy, and a strong or weak pawn structure can sometimes be the deciding factor in a game. The position of the pawns in turn determines where the other pieces should be placed.
Pawns are strong when they are connected - that is, when they stand on adjacent files so that they can protect each other. An isolated pawn is one that has no other friendly pawns on either side to protect it. Take a look at the board below.
White's pawns are connected together in a pawn chain. The pawn at the head of the chain is protected by its comrades. If the pawns were to advance together as a group, a different pawn could take the lead, and still be able to rely on another pawn to protect it.
Black's pawns, however, are all isolated. No matter how they advance, they can never protect each other, and if white had other pieces on the board, they could pick off black's pawns one by one. Another disadvantage of black's isolated pawns is that white could put a piece on the square in front of them, and black would never be able to use another pawn to chase it away.
Isolated pawns are weak, and you should try and avoid them while looking for ways to inflict them on your opponent.
A backward pawn is a pawn that, while technically a connected pawn, has lagged behind its comrades, and can't safely advance to catch them up.
Here, the white pawn on d3 is a backward pawn. It can't advance without being captured by the black pawn on e5. Note that the black pawn on d6 is not a backward pawn, as it still has the c7 pawn to support it, and the c7 pawn is not backward because it can safely advance.
Backward pawns are a lot like isolated pawns. They can be difficult to defend because no other pawns can protect them, and enemy pieces can sit on the square in front of them. Like isolated pawns, they should be avoided. When you advance your pawns, make sure you aren't leaving other pawns behind where they could become backward.
When a pawn captures a piece, it can sometimes end up moving to the same file as one of your other pawns, creating a doubled pawn.
After capturing the black pawn, white's pawns are now doubled. Doubled pawns are usually weak, because the pawn in front blocks the rear pawn from moving. They also cannot protect each other, and pawns that are doubled and isolated are especially weak.
You should take care that you don't let your opponent exchange pieces where you have to recapture by doubling your pawns and it could ruin your pawn structure. Take a look at the following example:
A passed pawn is a pawn that has no enemy pawns ahead of it which can stop it from advancing, either by blocking it or by capturing it. Take a look at the board below:
The white pawn on a5 is a passed pawn, because it has no enemy pawns ahead of it which can stop it advancing. The black pawn on d4 is also a passed pawn. The white pawn on f2 is not a passed pawn, because if it were to advance, it could potentially be captured by the black pawn on g6. Likewise, the black pawn on g6 is not a passed pawn because it could be stopped by the white pawn on h4 or the white pawn on f2.
Passed pawns are usually considered to be a strong asset, especially in the endgame, because they threaten to advance up the board and become a queen, and the opponent must use more powerful pieces to stop them, which in turn ties those pieces down to a passive role in defence.
At the start of the game, all eight of your pawns are connected in one long row. As the game goes on, and pawns get exchanged and captured, gaps start to open up in the pawn line. Each group of connected pawns is called a pawn island, and each isolated pawn is a pawn island by itself (although doubled isolated pawns only count as one pawn island). Take a look at the following board.
Let's count the pawn islands. White's isolated pawn on a3 is one island, the doubled isolated pawns on c2 and c4 count as one island, the connected pawns on f3 and e4 are one island, and the isolated pawn on h2 is one island, so white has four pawn islands in total. Black's connected pawns on a7, b7 and c6 are one island, and the connected pawns on f7, g7 and h5 are one island, so black has two pawn islands in total.
In general, it is always better to have fewer pawn islands, assuming you and your opponent have the same number of pawns (of course, it's not bad to have more pawn islands if you just happen to have more pawns). This is because a few larger groups of connected pawns are better able to defend themselves than many small groups. In the position above, we can see that black has the better pawn structure.
A pawn majority occurs when you have more pawns on one side of the board than your opponent does.
In this position, white has a three vs two pawn majority on the queenside, and black has a four vs three pawn majority on the kingside. A pawn majority is useful in the endgame, because it can make a passed pawn. If the white queenside pawns advance, and two of them are exchanged for black's queenside pawns, the remaining white pawn would be a passed pawn. Black could do the same thing on the kingside as well.
If your pawn majority contains a doubled pawn, your opponent may be able to blockade it with a smaller number of pawns. Take a look at this example:
Black has a crippled majority on the queenside. His four pawns are securely blockaded by white's three pawns. The white pawn majority on the kingside, however, is free to advance and make a passed pawn. This is another example of how doubled pawns can be a serious weakness, even if they aren't isolated.
Pawns cannot move backwards, so every time you move a pawn you are potentially relinquishing control of some squares that were guarded by the pawn before it moved. If you have other pawns that can maintain protection of these squares, then it's not so bad, but if you permanently give up pawn control over a square, it can become a hole.
A hole is like the square in front of an isolated or backward pawn. It cannot be guarded by a pawn, so enemy pieces can lodge there without fear of being chased away by pawns. On the board below, the crosses show squares that are covered by pawns, and the dots show the holes.
Note that the b4 square isn't yet a hole, because white could cover it by pushing the a2 pawn to a3. Suppose white made some more pawn advances:
See how the number of holes has increased! Of course, this doesn't mean that you should never advance any pawns, but it does mean you should think carefully about potential holes that might appear in your pawn structure, and whether your opponent can exploit them by putting pieces there. This is especially important when thinking about the pawns in front of your king. Leaving holes for enemy pieces near your king can be a deadly mistake. Remember this example from the checkmate tutorial?