A Codeword is a special kind of crossword: there are no clues and all of the answers are placed in the grid, but they are in code. Each letter of the alphabet appears at least once in the grid, and each has been substituted for a number, from 1 to 26.
In a Codeword puzzle, a single letter is always represented by the same number, wherever it appears in the puzzle. The challenge is to decipher the code. Two or three letters are usually revealed, to give the solver a head start. Only dictionary words are deployed (no proper nouns appear in the puzzles), so a good knowledge of English will help with solving the puzzles.