From shop records to reports
A retailer might copy sales records from its shop (extract), convert currencies and put dates into one format (transform), then put the prepared copy in a data warehouse for reports (load). This sequence is a type of data pipeline.
Prepare before or after loading
ETL prepares data before loading it. ELT loads data first and prepares it in the destination. Loading first can keep more original detail for later questions; preparing first can leave out information the destination does not need, including sensitive details. Both approaches need checks for missing or repeated records and shared definitions for reports.