Phonics is the relationship between the 26 letters of the English alphabet, and the approximately 44 speech sounds they represent, depending on dialect. The sounds of the English language are known as phonemes and the letters and letter combinations are known as graphemes. Grapheme-phoneme correspondences (GPCs) are represented by approximately 250 different spellings (Moats, 2010).

“Phonics: A system for approaching reading that focuses on the relationship between letters and sounds. Phonics helps with sounding out unfamiliar words”
Kilpatrick 2017
Phonics is essential for struggling readers, as well as students with learning disabilities including dyslexia, students with intellectual disabilities, and students for whom English is a second language.
Hempenstall (2016)
Of course phonics should not be taught on its own or in isolation. Phonics should be taught alongside phonemic awareness, fluency, vocabulary and comprehension every day in the beginning stages of learning to read.
FIVE from FIVE (2018)
The results reveal that phonics instruction is the most intensively investigated treatment approach. In addition, it is the only approach whose effectiveness on reading and spelling performance in children and adolescents with reading disabilities is statistically confirmed.
Galushka et al. (2014)
At the current state of knowledge, it is adequate to conclude that the systematic instruction of letter-sound correspondences and decoding strategies, and the application of these skills in reading and writing activities, is the most effective method for improving literacy skills of children and adolescents with reading disabilities.
Galushka et al. (2014)

The term phonics can also represent an approach to teaching of reading and spelling that emphasises directly teaching the relationship between speech sounds and the way they are represented in print, especially when it comes to early reading instruction.

Beginning readers need to be explicitly taught how our speech sounds map to the different spellings or GPC’s in a logical and sequential order, starting with the simple code (see below for an example). Once a few of these have been introduced, young children should be given opportunities to learn to blend them together to form words. Beginning readers should also be taught segmenting and phoneme manipulation.

Segmenting, blending and phoneme manipulation are essential phonemic awareness skills and once children start school these skills are best learned in conjunction with grapheme-phoneme correspondences or phonics.

There is overwhelming research evidence that demonstrates early reading progress is most likely to occur when the early reading instruction includes systematic and explicit teaching of phonics, especially for those children who are at greatest risk of reading difficulties. Phonics should not be taught on its own. Phonics should be taught alongside phonemic awareness, fluency, vocabulary and comprehension every day in the beginning stages of learning to read.