Copy activity is one of the most popular and universally used activities in the Azure data factory. It is used for ETL or Lift and Shift, where you want to move the data from one data source to another. While you copy the data, you can also do the transformation; for example, you read the data from the TXT/CSV file, which contains 12 columns; however, while writing to your target data source, you want to keep only seven columns. You can transform it and send only the required columns to the destination data source.
