Definition of Rollback and Roll forward?

Rollback: The Rollback transaction is a transaction which rolls back the transaction to the beginning of the transaction. The transaction can be rolled back completely by specifying the transaction name in the Rollback statement or to cancel any changes to a database during current transaction. It is permissible to use before Commit transaction.

Roll forward: Recovering a database by applying different transactions that recorded in the database log files. It is nothing but re-doing the changes made by a transaction i.e. after the committed transaction and to over write the changed value again to ensure consistency.