Acronym of ETL is Extract .Transform and Load . which is used in the data extraction ,data transformation as follows

What is Data extraction?

It extracts data from homogeneous or heterogeneous data sources.

What is Data Transformation?

It transforms the data for storing in proper format or structure for the purposes of querying and analysis.

What  is Data  loading?

It loads the data into the final target.

ETL does parallel processing like when extraction of data  occurs , another transformation process and loading the data at the same time as it saves much  time .