The examiner is looking for your essay to demonstrate 4 different aspects in order to get a good result: task achievement (have you completed the task?), cohesion and coherence (does your answer make sense?), lexical resource (have you used academic vocabulary?) and grammatical range and accuracy (is your grammar correct and have you shown a number of different structures?).
First is whether you have completed the requirements of the Task. That is, have you written at least 150 words but not more than about 170? Also in this section, the examiner will be looking to see if you have given an accurate description of the graph. Transferring information incorrectly will lose marks.
The second area the examiner will be looking at is whether what you have written actually makes sense. This means that when you plan and write your essay, you must have a logical presentation with ideas that are linked together. You should also have a clear sentence and paragraph structure.
For lexical resource, you are being judged on whether the vocabulary you use is accurate and academic. You should avoid repeating vocabulary – especially using words taken from the question title.
The final area you are being marked on is your grammar – again, you should use an academic level of grammar and avoid repeating grammar structures. In this course, you will have plenty of practice in order to improve your skills in all of these areas.