On OLAGE, we ask applicants to write a cover letter for the chosen program, that means a motivational letter or a statement of purpose. For what expectations ?
A motivational letter (or cover letter) is a letter in which you describe your current background, your career plans and how the ESA expected program will help you in achieving your professional projects.
You can show your motivation and reasons for applying in accordance with this program and the skills you already have.
On Internet, you can find some templates.