What is Data Lineage?
Data lineage traces where a piece of data came from, what transformations it went through and which reports depend on it.
Data Lineage explained
When a dashboard number looks wrong, lineage lets you work backwards: which table fed it, which query built that table, which source system supplied the rows.
It also works forwards: before changing a column you can see which reports will be affected. Even a simple written map of key tables and their sources helps.
Example
The revenue chart reads the monthly_sales table, which is built nightly from orders and refunds in the billing database.