Hi Joy, a PDF file is one that can be read by your Adobe Reader. As most people have Adobe Reader on their computer this is a great way of being able to share documents and pictures with different computer systems. For instance if I posted a file that was written using Microsoft Word you would only be able to read it if you also had the same program on your computer. Don't worry about it for this first lesson though, There are no PDF files to download, I was just making enquiries to see if people would find this useful