I'm going to assume that you are applying for a study abroad program.
The program I went through asked specific questions to answer in the essay, so I'll tell you what they asked:
What classes will you take while abroad, and why? Are they for your major, etc?
Why is this a good time for you to study abroad?
Why do you want to study abroad?
Have you traveled before?
What will you do once abroad? (ie- classes, volunteer)
I wrote mostly about my goal to become a doctor and tied in how studying abroad would help me achieve that goal/make me a better doctor and person in general...like gaining a more holistic world view/understanding differences between cultures and people and accepting everyone as they are.
