ETL is the process of extracting data from source systems and bringing it into the data warehouse. This stands for extraction, transformation, and loading. ETL refers to a broad process, and not three well-defined steps. The methodology and tasks of ETL have been well known for many years, and are not necessarily unique to data warehouse environments: a wide variety of proprietary applications and database systems are the IT backbone of any enterprise. Data has to be shared between applications or systems, trying to integrate them, giving at least two applications the same picture of the world. ETL software extracts data from the sources it wants to get them from. This software then proceeds to transform and modify such data forms to one that meets its operational requirements or needs. The final part of the ETL process involves loading it to the target data storage location which could be a database, mart for data, or a data warehouse. ETL software is often used to integrate and unify data from several applications at a time. Many of these applications are usually designed and supported by different companies or hosted on different computers. ETL applies several rules or logics to the data in order to facilitate its movement from one storage to another. The three processes of ETL can be designed and customized based on the needs of the organization using it.