Data engineering involves designing, building, and maintaining data warehouses to transform raw data into queryable forms that enable analytics. A core task of data engineers is Extract, Transform, and Load (ETL) processes - extracting data from sources, transforming it through processes like filtering and aggregation, and loading it into destinations. Data engineers help divide systems into transactional (OLTP) and analytical (OLAP) databases, with OLTP providing source data to data warehouses analyzed through OLAP systems. While similar, data engineers focus more on infrastructure and ETL processes, while data scientists focus more on analysis, modeling, and insights.