Phonics: the definition ...
Phonics – teaching children the sounds made by individual letter or letter groups (for example, the letter “c” makes a k sound), and teaching children how to merge separate sounds together to make it one word (for example, blending the sounds k, a, t makes CAT). This type of phonics teaching is often referred to as “synthetic phonics”.

Why is it important?

Phonics instruction teaches children how to decode letters into their respective sounds, a skill that is essential for them to read unfamiliar words by themselves.

Keep in mind that most words are in fact unfamiliar to early readers in print, even if they have spoken knowledge of the word. Having letter-sound knowledge will allow children to make the link between the unfamiliar print words to their spoken knowledge.

Another aspect that is rarely discussed is that the letter-sound decoding process itself is a learning mechanism. For example, make a mental note of how you feel when reading the following words:

Wingardium Leviosa

When you first read these words, you probably used your letter-sound knowledge, which involved two important processing stages:

1) It helped you produce the correct sound of an unfamiliar print word. If you’re a Harry Potter fan, the pronunciation also probably lit up connections to the meaning of the word.

2) It drew your attention to the details and the combination of the letters of the word.

These two steps then function as a learning mechanism, allowing you to recognise the previously unfamiliar word quicker the next time around (go back to read the words again and see how you feel about them now).

This transition from slowly sounding out a word, to rapidly recognising it, is what we call “learning to read by sight”. Every reader must make this transition to read fluently.