Backup: A backup is a copy of a computer system's files and settings stored externally. This means data can be recovered in the event of data loss. Data loss can happen for many reasons (fire, theft, flood, malware, hardware failure, or user error). A backup utility is software with facilities such as scheduling of regular backups, creating rescue disks, disk images, and options for full or incremental backups: Full backup - where a copy is taken of every file on the system. They often use a lot of storage space. A full backup can take a long time to create, but it is faster to restore from; Incremental backups - where only the files created or edited since the last backup are copied. They use less storage space and are much quicker to create. But, a full system restore is slow. The last full backup must be restored, followed by every incremental backup since that point.