A full backup creates a complete copy of the target data. It does not take into account changes since the last backup, it simply copies everything. Due to this it is the slowest to backup, but the fastest to restore when needed. Incremental backups are quicker to capture as they only backup changes since the last backup occurred. Differential backups are similar but only take into account data that has changed since the last full backup (ignoring any incremental backups in-between).
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