What is a PDF file, and what does it do?

Hey so my task in class was to find out what a PDF file was so I decided to go to the Adobe site and take a look and here is just a brief overview from what I read on the site :)

PDF (Portable Document Format) is a standard in electrical document exchange. When you convert documents, graphics, forms, and webpages to a PDF file, they look how they would if printed but PDF has clickable links and buttons, forms fields, videos and audio, as well as logic to help automate routine business processes.