PDFs

This may sound like a stupid question, but what is an Adobe PDF????

Portable Document Format. Another type of document file to the average person, like Word documents or HTML, if you like, except better, since it has much more cross-platform support and can look nicer than either. It's used mainly for sharing/sending/providing information rather than for stuff that needs constant editing like text files, e.g. you'd probably save your work in this format if you needed to take a copy to the local publishers for mass printing a book or posters, or providing downloadable online manuals for games/hardware/whatever, or forms for printing and filling out. You can get a reader for Windows from www.adobe.com if you need to read one of these files.