The key to understanding what data engineering lies in the “engineering” part. Engineers design and build things. “Data” engineers design and build pipelines that transform and transport data into a format wherein, by the time it reaches the Data Scientists or other end users, it is in a highly usable state. These pipelines must take data from many disparate sources and collect them into a single warehouse that represents the data uniformly as a single source of truth.
Sounds simple enough but a lot of skill goes into this role. This is why Data Engineers are in such short supply and why there is confusion around the role.