Phonics is a method of teaching young learners how to read which focuses on how letters make sounds, and how these sounds make words. It can be compared with the whole word, or 'Look and say' approach, which focuses on recognising words.

Example
Using a phonics approach, the word 'cat' would be read aloud by reading the letters c - a - t.

In the classroom
There are many arguments about the best way to teach children how to read. Some schools use an approach that mixes elements of the phonic and the whole word methods, or uses one and then the other.

Further links:
https://www.teachingenglish.org.uk/article/reading-young-learners
https://www.teachingenglish.org.uk/article/first-class-very-young-learners