ETL is an abbreviation for Extract, Transform, Load. It is the process of extracting data from various sources and transforming it into a predefined format before loading it into a data warehouse. This is done either periodically or on an event-based model (e.g., whenever there's a new purchase order).
ELT stands for Extract, Load, and Transform. The data extraction happens first as described above; then the transformed data is loaded into the warehouse, and lastly, there's some kind of transformation or manipulation done to this loaded copy before being made available for use by end users who are part of your organization's business intelligence team or other stakeholders who need access to this information in order to perform their job functions effectively.