Shodan
A search engine that continuously indexes internet-connected devices and the services they expose.
It lets anyone search for exposed remote desktop, databases without authentication, industrial controllers, and cameras, filtered by organization, location, or software version.
It is used by defenders to find their own forgotten exposures and by attackers to find targets running a newly exploitable version. Checking what it says about your own address space is a worthwhile hour.
Where this comes up
Shodan sits inside our penetration testing work. If you are trying to work out what this means for your own environment rather than in the abstract, that is the page worth reading next, and a short call will get you a straight answer faster than either.