ETL (Extract, Transform, Load) is a process used to move data from various sources into a data warehouse or database for analysis. The ETL process consists of three main stages: extraction, where data is retrieved from source systems; transformation, where the data is cleaned, enriched, and converted into a format suitable for analysis; and loading, where the transformed data is loaded into the target data repository. ETL is essential for integrating data from disparate sources, ensuring consistency and quality, and preparing data for business intelligence and reporting. It supports efficient data warehousing by streamlining data preparation and enabling complex analytical queries.