You must use an external drive or burn all of your content onto CD's/DVD's which is a bit of a pain compared to using an external hard drive.
External hard drives are relatively inexpensive these days and its a great idea to backup everything on your computer. It would be advisable to purchase one and start backing up everything on your computer.
The article you just read describes how to back up your iOS device.
This one is more relevant:
Do not rely upon your iPad to back up your non-iTunes purchased music. It is not designed to do that. Back up your iTunes Library to an external device.
Better yet, back up your entire Mac using Time Machine or "clone" software.