Have you considered using the backup software included with your OS (which you didn't specify)? If Windows, it can be automated through Task Scheduler. For commercial software, check the reviews at http://data-backup-software-review.toptenreviews.com/.
Sync software is to synchonize files between two storage areas, e.g., the local hard disk and a server share, a folder on your hard disk and a USB key, two folders, etc
While they can technically overlap a sync programs (like SyncToy - free and really quite nice) generally work at the file level and will keep your files in two locations duplicated.
Backup software usually makes a copy of your current data to a different location, but does not overwrite that location unless you tell it to...it's a point in time copy.
Backup software like Acronis and others that make images do a block based copy of the install, I believe. They then can restore those blocks to another device like it was the original.