One of the most common early mistakes students make in their essays is to write descriptively rather than analytically.
What is descriptive writing? This is when you make passive observations about something and note them down. There is no in depth interaction with the observation. It is presenting information but not transforming it. When you write descriptively, you don't really have a point.
Analytical and critical writing require interaction with the information. Analytical writing includes descriptive writing (i.e. facts or information), plus the added feature of re-organisation and analysis.
Below is an example of the difference (it's ok if you don't know the book!):
Question: How does Harper Lee construct the character of Scout?
Descriptive:
Scout is constructed as a very innocent character. This is evident as she does not understand a lot of the insults that other people use. She also speaks her mind and does not think very deeply about the situation and takes it at face value. This shows that she is a very naive individual.
Note how the above paragraph simply lists events that have occurred without truly processing that information. It describes what can be taken from just reading the words of the book rather than delving into the underlying message. This lacks depth and hence, would receive lower marks.
Analytical:
Scout is constructed to have a very innocent view of the world. In the court room scene, Scout found the trial boring as "nobody had thundered, there were no arguments between opposing counsel, there was no drama". The asyndeton creates a dull listing effect that amplifies Scout's perception that the case was dull without understanding the underlying tensions. Her view that Atticus was making "a rape case as dry as a sermon" creates a jarring effect through the juxtaposition of crime and religion. The simile illustrates her lack of insight into the severity of the situation and the resultant light hearted tone brings forth her naive nature.
In contrast, this paragraph is focused on breaking down how the words used held underlying meanings that contributed to the argument. It takes observations and turns them into ideas and analysis.
Hopefully the example clearly contrasted the difference between analysis and storytelling. Next time you are told that you were storytelling, come back and refresh your memory before delving into that essay again!