This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.
ETL is important, as it is the way data actually gets loaded into the warehouse.
A good ETL tool must be able to communicate with the many different relational databases and read the various file formats used throughout an organization.
ETL tools have started to migrate into Enterprise Application Integration, or even Enterprise Service Bus, systems that now cover much more than just the extraction, transformation and loading of data.