BACKUP is different than REPLICATION because backup saves a copy of data for a long period of time. Replicas are updated frequently and quickly lose any historical state. Data Replication is written in a format that is understood by your database and applications. Disk Backup needs to be written in a format that is understood by the backup application- which in the case of a disaster would require a restore of the data in order to access it. Replication is transparent to the end user. In the case of a disaster a failover of replicas is hidden as much as possible.
Load balancing - Load Balancing is different than task replication since it distributes a load of different computations across machines and allows a single computation to be dropped in case of failure. Load balancing does however use data replication (multi-master) internally to distribute its data among machines.