Letter-sound correspondence is the understanding that written letters represent specific spoken sounds. The letter "m" makes the /m/ sound; the letter "s" makes the /s/ sound. This alphabetic principle is the bridge between knowing letters (visual) and hearing sounds (auditory), and it is the essential insight that unlocks reading. Children learn first with consonants that have consistent sounds, then move to short vowels and common digraphs (sh, th, ch).
Teach one or two letter-sound pairs at a time using a keyword picture (a = apple, b = ball). Practice with sorting activities ("Put the pictures that start with /b/ in this pile"). Use decodable texts that contain only the letter-sound relationships the child has learned. Multisensory practice -- saying the sound while tracing the letter -- strengthens the connection.
You already know two things that are about to connect: you can recognize what letters look like (letter recognition), and you know that spoken words are built from individual sounds that can be isolated and played with (phonemic awareness). Letter-sound correspondence is the bridge between these two kinds of knowledge — the discovery that the symbols you can identify visually stand for the sounds you can hear and manipulate. This is the alphabetic principle, and it is arguably the single most important insight in learning to read: writing is not magic or a collection of shapes to memorize; it is a code for speech.
Think of letters as keys on a keyboard and sounds as the characters they produce. When you press "M," you get /m/. The letter is the symbol; the sound is what it represents. English uses 26 letters to represent approximately 44 phonemes (distinct sounds), which means the code is not perfectly one-to-one — some letters represent more than one sound (the letter "c" can be /k/ as in *cat* or /s/ as in *city*), and some sounds are represented by letter combinations called digraphs (like "sh" for /ʃ/ or "th" for /θ/). But the code is regular enough that learning the core grapheme-phoneme correspondences — the relationships between written symbols and sounds — unlocks the ability to attempt new words you've never encountered in print.
The sequence in which letter-sound correspondences are taught reflects what phonemic awareness prepared you for. Because you can already isolate the first sound in a word, initial consonant sounds are learned first — they are the most audible and easiest to isolate. Short vowels come next, enabling consonant-vowel-consonant words like "cat," "dog," and "sit" — the earliest truly decodable words. Digraphs and long vowel patterns come later, because they require understanding that the code sometimes involves more than a simple one-letter-to-one-sound relationship. Every new correspondence you learn expands the range of words you can read without memorizing them individually.
The payoff of mastering letter-sound correspondence is decoding — the ability to translate any string of letters into a pronunciation, even for words you've never seen before. This is why phonics instruction is foundational: once you possess the code, you can attempt any word. Words that are genuine exceptions to the code ("said," "the," "was") become sight words — memorized as whole patterns — but these are the minority. The vast majority of written English is decodable by someone who knows the core correspondences. Letter-sound correspondence is not the end of reading; it is the door that opens onto fluency, vocabulary, and comprehension. Everything that follows — reading independently, encountering unfamiliar text, building vocabulary through print — depends on having cracked this foundational code.