Answer:
When they are concise and humorous.
Step-by-step explanation:
An example of my teacher being this way is when my teacher is teaching Life of Pi. When she explains the way that Pi must be feeling having a tiger, an ape, a hyena, and a dying zebra all on one lifeboat, she makes it clear to us how stressing it would be to be in that situation, while making it funny by showing the lighter side of things.