Integration Services uses transformations to manipulate data during an ETL dataflow. Transformations can be used in Data Flow Tasks, between data source and destination components, or other transformations.
The Unpivot transformation can help in normalizing of a dataset during the load process of a data warehouse.
For example, if the source dataset looks like this (five columns):
So, the Unpivot transformation can be used for the normalization of a dataset on the fly - unlike the Pivot transformation, which is helpful when a denormalized result set is needed.
For more detailed information on this transformation, please refer to this MSDN article.
For the complete list of SSIS transformations, check this Wiki article.