Hello all. I have a question about the Headlines module on my site. When I try to add a headline, it asks me for the URL of RDF/RSS file. What is this and where do I find it? Also, is there a way to uninstall a module or do I just have to make it not visible? Thanks in advance!

RDF/RSS files are a kind of XML files which content is generated automaticaly with the recent news of a news site/blog/forum/etc for example. You have to give its link to the headline module so it to display the headlines it has on your page. As xml files RDF/RSS typically has an rdf/rss/xml extention, or can be generated by a script language like php, etc.
To uninstall a module you go through 2 steps - first make it inactive and second uninstall it. You do it from your Administration modules preferences page.
Take a look at XOOPS FAQ here on XOOPS org or search for some XOOPS tutorials mentioned here around, like XOOPS for Dummies! There you'll find the answers of a lot of questions.