The “data” part of the terms “data lake,” “data warehouse,” and “database” is easy enough to understand. Data are everywhere, and the bits need to be kept somewhere. But should they be stored in a data warehouse, a data lake, or an old-fashioned database? It all depends on how that data is going to be used.
It’s difficult to define the names precisely because they are tossed around colloquially by developers as they figure out the best way to store the data and answer questions about it. All three forms share the goal of being able to squirrel away bits so that the right questions are answered quickly.