What is On-premises
Running software on servers a company owns and operates itself, in its own building or rented rack space, instead of the cloud.
In plain terms
Before cloud providers, every company ran its software this way, and many still do. Banks, hospitals, governments, and manufacturers keep systems on-premises for regulatory, security, or cost reasons. Bare metal means running directly on the physical machine. Many job descriptions describe hybrid setups, part on-premises and part cloud, or migrations moving systems from one to the other.
What it tells you about a developer
On-premises experience is common in finance, healthcare, government, and older enterprises, and it runs deep. Someone who has operated their own hardware understands networking, storage, and capacity at a level the cloud abstracts away, so the cloud's concepts map cleanly onto what they already know. Developers who have run a cloud migration have seen both worlds, which hybrid-infrastructure roles specifically want.
Related
Read the lesson on On-premises More in How software gets built