Learn in the textbookFile System Basics — Directory Management and Backup
DefinitionA backup (バックアップ) is a copy of data kept on a separate medium or in a separate place, in case the data is lost through a failure, a user's mistake or a disaster.
ExplanationBringing lost data back from a copy is called a restore (リストア, also 復元). Methods include, for example, a full backup (フルバックアップ) that copies everything, a differential backup (差分バックアップ) that takes the changes since the last full backup, and an incremental backup (増分バックアップ) that takes only the changes since the previous backup.
AnalogyIt is like leaving a spare house key with a relative who lives somewhere else. Even if you lose your key at home, the spare one gets you back in.
Memory hookTo "back up" someone is to support them from behind. The copy stands behind the original data, ready to step in.