If I'm remembering right, and you're talking about the AACOMAS personal statement, they tell you specifically to answer two questions (that pretty much sets the short essay up for you- don't worry you'll have plenty of room on secondaries to elaborate). I think they questions are: provide motivation for osteopathic medicine and discuss your goals, or something similar to that. That's what I wrote my essay on and then I expanded on those topics in my secondaries. 🙂