Decoding is the ability to sound out words by sound-letter correspondence and blend sounds so that written text can be recognized and interpreted. This is a key component of phonological awareness and processing, and is a foundational skill for reading.
Individuals who struggle with decoding will often make errors that are logical guesses based on context and not really reading the word. Alternately, they will rely on their memory skills, which will work for sight words and familiar text; however, if they do not have the ability to decode, then breakdowns will become very apparent when presented with new and more complex vocabulary that need to be sounded out.
When a child struggles to decode or sound out words, he/she will often demonstrate difficulty comprehending what they have read. These individuals put tremendous effort into sounding out the words, and as a result, may miss the content of the written piece.