The document discusses the pronunciation of the letter C in Catalan words. It notes that C sounds the same in words like CASA, COR, and CUINA, but sounds different in words like CELLA and CISTELL when followed by E or I. To make the C sound as in CASA before E or I, the letters QU must be written instead of C. Examples are provided like QUEIXAL and QUINZE to demonstrate this spelling rule.