Phonetic rules are guidelines that describe how sounds in a language are produced and organized. These rules help explain how different sounds can change based on their position in a word or the sounds around them. For example, the pronunciation of the letter c can vary, sounding like /k/ in "cat" and /s/ in "city." These rules are essential for understanding phonetics, the study of speech sounds, and phonology, which focuses on how sounds function within a particular language. By following phonetic rules, language learners can improve their pronunciation and comprehension, making communication clearer and more effective.