Your reasons for applying will give your interviewers a sense of whether they can provide you with an internship in which you will thrive and feel motivated to perform well. You may have answered this question in your application. Expand on it. Tell recruiters what you really want to get out of the internship. Think about how it will inform your graduate career choices, what skills you are keen to learn from it and other things that appealed to you when you read the role description.