ETL is sort for extract, transform, load, three db functions that are combined into one tool to pull data out of one db and place it into another db.
• Extract is the process of reading data from a db
• Transform is the process of converting the extracted data from its previous form into the form it needs to be in so that it can be placed into another db. Transformation occurs by using rules or lookup tables or by combining the data with another data.
• Load is the process of writing data into the target db.
ETL is used to migrate data from one db to another, and also to convert db from one format or type to another.