About Postgres
The database most business applications run on.
PostgreSQL started at UC Berkeley in 1986 and has been open-source since. It is ACID-compliant, extensible and used as the primary operational database behind a very large share of custom-built business applications, from internal tools to SaaS backends and ecommerce platforms. When your engineers built something important and picked a database, the answer was almost always Postgres.
The point of pulling Postgres into a warehouse is that reporting directly on the application database is slow, risky and quickly becomes wrong. Schemas change as developers ship features, large joins compete with live traffic, and the weekly dump someone set up two years ago now powers half the dashboards. In a warehouse, the application's Postgres becomes a first-class source next to Salesforce, Exact Online, Shopify and Stripe, without putting reporting load on the database that has to stay up.