Doing multiple operations atomic is one of the fundamentals of each application which works with data. Many applications have transaction support; transactions are operations that will be run as one unique atomic operation. An atomic operation means that all operations will be run successfully or if an error happens and one of them caused the error all of them will rollback.
SSIS supports transactions also, but SSIS transaction differs from database transaction. SSIS can do most of the tasks atomically, you can copy files from source place to destination, extract them, transfer them to database, and if any error occurs you can rollback all operations.
SSIS uses the Microsoft Distributed Transaction Coordinator service (MS DTC) for transactions. Microsoft applications use this service for handling their transactions, for example you will see that WCF uses this service for managing transactions also. So for using transactions in SSIS this service...