Final answer:
In a data warehouse, the process of collecting data from various sources and formatting it for transformation is called extraction. It is the initial phase of the ETL process.
Step-by-step explanation:
In a data warehouse, the process of collecting data from a variety of sources and converting it into a format that can be used in transformation processing is known as extraction. This is the first step in the Extract, Transform, and Load (ETL) process, which is fundamental to the functioning of data warehouses. The extraction process involves taking data from different source systems, which may include databases, ERP systems, flat files, APIs, and more, and then placing it into a staging area where it can be transformed into a common format or structure.