What's the difference between a cover letter and a statement of interest?

I'm a first-year university student looking for research internships this summer. I applied to a few internships at one lab and submitted a resume and cover letters for each. A few days later they contacted me and asked me to make a profile on their website and supply some more information. They asked me to provide a "general statement of interest which will be shown for applications". I'm not sure how this is different from a cover letter, except that apparently I can't tailor it to specific internships. How should I write this so that I'm not just restating my cover letters?

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