I think the word you're looking for is 'abstract,' and not preface. I might be wrong in your case, but typically prefaces are much longer than 80 words.
What I would do would be to take those 80 words and summarize the major research and findings in your paper to the common person, whom you assume knows nothing. Meaning that it should be watered-down to a degree, but also hit upon the main themes of your paper, problems you encounter, methods to try and solve such problems (or answer proposed questions), and then a hint at your results.