Explain in your words the difference between these two concepts:

Prequalifying
Preapproval
How would you explain this to your principal (you represent the buyer) and convince them to do both?

2 answers

Since I'm not in your class, I assume your teacher wants YOUR words, not mine.
I hope you are 100% sure of what each of those words means. If not, be sure to look them up at http://www.onelook.com

Once you are clear on their meanings (and how they are different from each other), you should be ready to write your response.