I have heard of a few types of of pawns, such as passed pawns, thorn/fawn pawns, promoted pawns, and en passant pawns. But that is all I can remember. What other types of pawns are there?
Backward pawn: a pawn that is behind its colleagues on a pawn chain. It cannot safely advance because it will be captured. These pawns are often a liability because they can be attacked. Example:
8/8/8/3p4/3P1P2/4P3/8/8 w - - 0 1
The pawn on e3 is backward. If Black e.g. places rooks on the e-file, White will have to guard the pawn with pieces, which is passive. Black also has a "captured square" on e4 where he can station his pieces and they cannot be pushed away by White's pawns.
Central pawn: a pawn on the two central files (d- and e-files). Compare "flank pawn".
Connected passed pawns: see passed pawn. Being connected means there are two passed pawns of the same color on two adjacent files. This is almost always a very strong trump.
Doubled pawns: two pawns on the same file. This is sometimes bad because they are inflexible. They can, however, guard key squares in the middlegame. Compare "tripled pawns".
Flank pawn: a pawn on the sides of the board (the a-c files and the f-h files). During the middlegame they usually less valuable than a central pawn because central control is an important tenet of chess strategy. Compare "central pawn".
Hanging pawns: two adjacent pawns side-by-side, with no other pawns on the adjacent files. They guard squares and mark out space. Example:
8/8/8/2pp4/8/8/8/8 w - - 0 1
Black's two pawns (note no pawns on b- and e- files) are hanging pawns. Black will try to keep them in place since they control squares, while White will try to force one of them to advance. If White succeeds, then the Black pawns leave behind a hole, e.g. if Black is forced to play ...d4, then the c4-square becomes a weak square White can occupy.
Isolated pawns: a pawn without a friendly pawn on its adjacent files. These are usually a liability because if they are attacked, they have to be defended by pieces, not pawns.
Outside passed pawn: see also "passed pawn". This refers to a passed pawn that is far away from the action. For example, if there's an ongoing Kingside attack, then any passed pawn on the queenside would be extra valuable, because the defender needs to balance between using its pieces on the kingside and using them to restrain the pawn.
Passed pawn: a pawn that has no enemy pawns that are in front of it on its same file as well as on files to its left and right. These are generally trumps because the opponent needs to use pieces to stop them from queening.
Thorn (fawn) pawns: as far as I know, this terminology only exists in the computer chess community. They refer to protected pawns on the 6th rank that are blocked by another pawn. Example:
6k1/5p2/4pPp1/4P3/8/8/8/8 w - - 0 1
The White pawn on f6 is a "fawn". It attacks an important square around Black's king, and also makes e7 (usually an important square for Black's pieces to maneuver) inhospitable. Black would love to be rid of it, but it's protected by the pawn on e5. That makes it a "thorn" in Black's position. As far as I know, "fawn" came about as a mispronunciation of "thorn".
Tripled pawns: three pawns on the same file. This is almost always bad because they can be easily attacked and none of the pawns can defend each other. Compare "doubled pawns".
passed pawns: When there is no enemy pawn on the adjacent file(s), it's called a passed pawn.
Promoted Pawn is when one player's pawn goes to the end of the enemy camp and you can choose a piece (Queen, bishop, rook, knight) you wish (except the king or a pawn itself)
en passant: Better to show with an example
Isolated pawn: When you don't have any pawns in the adjacent file but there are enemy pawns either on the same file or on the adjacent ones.
There are more pawn types i.e. Isolated queen pawn, hanging pawns but for a beginner it's hard to explain and it's not too relevant if you play chess for fun.