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.

Alphanumeric values are often need transformation during a data flow: converting to upper- or lowercase is the most common case. This can be solved using the Derived Column transformation as well - in combination with the UPPER or LOWER functions.

But Character Map has other features as well: reversing byte order, mapping katakana characters to hiragana characters (and vice versa), mapping half width characters to full width characters (and vice versa). There is an additional transformation - linguistic casing -, which uses an external reference to the Win32 API for Unicode simple case mapping of some locales.

The Character Map transformation supports an input, a regular and an error output.

For more detailed information on this transformation, please refer to this MSDN article.
For the complete list of SSIS transformations, check this Wiki article.