Congrats... Probably a bunch of research/writing, and drafting court orders. Basically a lot of the stuff from your 1L Legal Research/Writing class.
Don't worry about not having asked what you will be doing to the judge/clerks. Because of the hurried timeframe of applying for these jobs, 1Ls have to do it pretty fast without thinking much about the actual work. But its a great experience, enhances key skills, and (most importantly) is looked upon extremely favorably by employers - especially working for a federal judge!