ETL - extract, transform and load - is the set of processes by which data is extracted from numerous databases, applications and systems, transformed as appropriate, and loaded into target systems - including, but not limited to, data warehouses, data marts, analytical applications, etc.

More than half of all development work for data warehousing projects is typically dedicated to the design and implementation of ETL processes. Poorly designed ETL processes are costly to maintain, change and update, so it is critical it is to make the right choices in terms of the right technology and tools that will be used for developing and maintaining the ETL processes.