SQL Server Integration Services (SSIS) is a platform for building high performance data integration and workflow solutions. It allows creation of packages or SSIS packages which are made up of tasks that can move data from source to destination and alter it if required.
SSIS is basically an ETL (Extraction, Transformation, and Load) tool whose main purpose is to do extraction, transformation and loading of data but it can be used for several other purposes for example, to automate maintenance of SQL Server databases, update multidimensional cube data etc as well.
via SQL Server Integration Services an Introduction – Part 1 – SQL Server Performance.