There exist many types of chess compositions. Those problems that obey the rules of a chess game are called orthodox compositions, and all the rest are called heterodox compositions.
The orthodox compositions are distinguished in problems, which have an upper limit on the number of moves in their solution, and in studies, which resemble normal game endings and where a limit in the number of moves is not specified.
The problems with a limit at two moves are called two-movers. The white plays first, then the black defends, then the white gives mate. The succession of the moves is W – B – W.
The problems of three moves are called three-movers. The succession of the moves is W – B – W – B – W.
The problems with more than three moves are called more-movers.
People practising chess gamrs prefer to solve studies. It has been observed that knowledge of the themes of the chess problems is very useful for the tactical part of the game.
A large group of problems have normal chessmen on normal chessboards but the two opponents are not trying to win.
In the helpmate problems black plays first and help white to give mate. The succession of the moves is B – W – B – W.
In the selfmate problems white plays and forces the black to give mate. The succession of the moves is W – B – W.
There are problems with series of movements, where the opponents are not playing alternately. For example in a series helpmate in seventeen, the black plays seventeen moves and then the white makes one move giving mate..
The problems which are completely out of the normal rules of the game belong to thn Fairy chess. The chessboard may be different, the normal chessmen may follow different fairy conditions, the chessmen may be fairy pieces. A lot of fairy conditions have been introduced, more than a thousand fairy pieces, and the production of new faity themes is strong.
In another group of problems, the retros, we are interested in the moves from the initial arrangement of the 32 regular pieces upto the position of the problem. For example, we try to find the shortest Proof Game which leads to the given position of the problem.
There are many elements which we will describe later. One thing is certain though, the imagination of the problemists is exceptionally fertile.
Semantics of words
The word Orthodox means the person who believes that his opinion is correct.
The word Heterodox characterizes the person having a different opinion.
In chess problems, when the position is a result of white/black playing alternatively from the initial arrangement of the 32 pieces and trying to win, then the problem is called orthodox.
Problems with different aim, different rules, different pieces, not alternative playing, and different chessboards, are called heterodox.
[This Post in Greek language]