Although pawns are the weakest piece, a large part of the nature of any chess position lies in how the pawns are placed. Sometimes, good pawn placement can win a game and compensate for a material deficit. How do you describe the pawn structure though? Let’s find out!
1. Connected pawns
Connected pawns are pawns of the same colour on adjacent files, meaning they can defend each other. In the endgame, connected pawns are very strong and can oftentimes promote.

2. Isolated pawns
Isolated pawns are pawns that cannot be supported by friendly pawns. Typically, these pawns are weak and easily attacked by other pawns/pieces.

3. Doubled/Tripled pawns
Pawns become doubled or tripled after they capture onto the same file. This type of pawn structure is disadvantageous, as the pawns cannot support each other. They also impede the movement of pawns behind it and are difficult to defend. Note that 2 pawns of different colours on the same file are not considered doubled pawns. When doubled or tripled pawns are isolated, they are even more of a liability, as they cannot even rely on/support neighbouring pawns.

4. Backward pawn
Backward pawns are pawns that are behind the pawns on either side of them. This means that they can't be defended by another pawn without capturing or moving forward, creating a weakness that your opponent can exploit. A common way to take advantage of a backwards pawn is to move a knight in front of it.

5. Pawn Majority/Minority
As the term suggests, a pawn majority means that you have more pawns than your opponent on either the kingside or queenside. Likewise, a pawn minority means that you have fewer pawns than your opponent on a certain side of the board. Note that it is possible to have pawn majority/minority on BOTH sides of the board.

6. Pawn Islands
Pawns islands are groups of connected pawns.

7. Pawn Storm
When you use your pawns to attack the opponent’s king (which is usually castled), it is called a pawn storm. If ignored, a pawn storm can open the king’s position and expose it to attack.

8. Passed Pawn(s)
A passed pawn is a pawn that cannot be stopped/captured by any pawns on adjacent files. These pawns are especially likely to promote.

All Images were created on chess.com.