A data pipeline is a system where data is transferred from the source to the target. Meanwhile, ETL – short for Extract, Transform, Load –  is a part of a data pipeline.
ETL is the process of transferring data from a source (i.e., a website), to a destination, typically a data warehouse. Extract refers to acquiring data from the source; transform refers to modifying the data for loading it into the destination, while load is the process of inserting the data into the storage unit.