Teaching students the correspondence between written letters (graphemes) and speech sounds (phonemes). For example, the words me and pony have the same sound at the end, but use different letters.
There are varying different kinds of phonic approaches with strong debate as to the merits of each. Research suggests that the particular phonic approach taken is not as important as the fact that a phonic approach is, in fact taken. Although the synthetic phonics program may differ the underlying methodologies are the same. The following quotes are instructive: