What is Data Lake?
A data lake is a storage area that holds large amounts of raw data, structured or not, in its original format until someone needs it.
Data Lake explained
Where a warehouse requires you to decide the structure first, a lake lets you store files as they arrive: CSV exports, JSON logs, images, event streams. The structure is applied later, when the data is read.
That flexibility makes lakes cheap and good for data science and archives, but it also means quality and meaning are not enforced. Many teams therefore load the useful parts of a lake into a warehouse, or put a query layer on top of the lake.
Example
A product team stores every raw app event as JSON files in cloud storage. Analysts later pick out sign-up and purchase events and load them into tables for reporting.
How it differs from similar terms
A warehouse holds cleaned, structured tables; a lake holds raw data of any shape.