Its essentially 50% self reflection 50% telling them about why you want to do the course.
Think about why you want to go on this summer course.
If its something like I want to learn Japanese then break it down further.
Why do you want to learn Japanese, anime, no dramas, j dramas, you want to marry a japanese guy, a challenge, become a translator…
Identify a target something you want to do and then say how you will get there, e.g. taking this summer course will allow me to reach my goal by etc.etc.
Link together your wants desires, etc. to their course, explain how their course will help you achieve etc.