What is the difference between "outline" and "explain" in an exam?

Outline - 'you need to describe and explain, but more description than explanation.'
Explain - 'give reasons why something happens.'

So outline is describe and explain, whereas explain is just explain? For example, if you were given a graph and it asked you to outline it, then you would describe the general trends etc, and then explain why the trends are like that. But if you were asked to explain the graph, then you wouldn't need to tell the examiner what the graph looked like.

Hope that made some kind of sense? Good luck for your exams!