What is Data lake
A store of raw data in every format, kept cheaply at full size so it can be analyzed later.
In plain terms
A data lake collects data exactly as it arrives: logs, events, exports, images, whole database copies. It lives in object storage, so keeping everything is cheap, and structure gets applied later when someone asks a question. Companies build lakes when data outgrows what a warehouse economically holds. The lakehouse pattern adds warehouse-style tables on top.
What it tells you about a developer
Data lake experience marks a data engineer, the person who builds the plumbing that moves and stores raw data at scale. It usually comes with pipeline tools, big-data processing, and cloud storage depth. It sits on a different rung of the data stack than warehouse and SQL analytics work, and the two are worth telling apart on any data req.
Related
Read the lesson on Data lake More in Who does what on a team