phonics: using sounds made by individual letters and groups of letters to read words
decoding: using your phonics knowledge to sound out real words
grapheme: a written letter or group of letters, like 's' 'a' 'ng' 'air' - some graphemes are single letters, others are digraphs (2 letters one sound) or trigraphs (3 letters one sound).
phoneme: the sound a letter or group of letters make - eg the word 'mat' has three phonemes. The word 'through' is longer but also has three phonemes 'th' 'r' 'ough'.
sounding out: using your phonics knowledge to help you say each sound within the word eg 'r-e-d' or 's-au-ce-p-a-n'.
blending: running the sounds in the word together to read the whole word
high frequency words (also known as 'common exception words') the very common words which we use a lot, but which aren't always decodable using phonics. Children are taught to recognise these words on sight - a few at a time.