Writing assessment in IELTS is based on four main parameters;Task achievement , Lexical resources , Coherence & Cohesion , Grammatical Range & Accuracy
Your score depends on how logically you have organised & connected your ideas , progression , sequence and the word range used. Sentences that fail to convey message , data redundancy , copying the question ,inappropriate words or ideas, punctuation & spelling errors are the common mistakes in tjis section.