Image backups, also known as Windows Image Backups or Windows Server Backup, is a backup of the full hard drive from the block level. It includes a backup of the operating system, all your installed programs AND all the files created with those programs.
"I’ve seen this multiple times. People leave their external backup drive connected to their PC and it runs continuously forever then dies after a year or 2. You should only connect it when you want to backup your files then disconnect it." -GCS Engineer