In plain language
It is the pipeline that turns scattered app data into consistent, report-ready tables.
Example
A nightly job extracts orders from Shopify, converts currencies and dates, and loads the results into a reporting database.
Related terms
Data Mapping · Sync (One-Way and Two-Way) · Batch Processing · Data Validation
Common misconception
ETL is not just copying data; most of the value and risk is in the transform step, where business rules are applied.
Implementation guidance
Document every transformation, keep raw extracts for reprocessing, validate row counts and totals after each load, and make reruns safe.