What are ETL tools? Why are they critical to most large organizations? Why are they important in order to create quantitative models such as multiple linear regression? Solution ETL stands for \"Extract/Transform/Load\". These tools take data from one source and move it into another. You can map schemas from the source to the destination in unique ways, transform and cleanse data before it moves into the destination, and load the destination in an efficient manner. List of the most popular ETL tools: These are the issues with data warehouse testing:-.