What is ROS?

ROS (Robot Operating System) is a framework that facilitates system development around robots by using abundant existing software.
It was also developed to support software reuse, and is designed to standardize hardware control methods and data so that different manufacturers and methods can be treated in the same way.

Although it is named as an operating system, it is a group of applications that run on the OS (mainly Ubuntu) as a software format, unlike what is generally called an OS such as Windows and Linux.