It is surprisingly hard to find out what this "ROS 2" thing is. It appears to stand for "robot operating system". The tutorial talks about "interfacing with ROS 2" from your ESP32 microcontroller, or rather from code you run on your microcontroller.
So I am guessing that it is a firmware system preloaded and running on microcontrollers built into robot hardware that your own code, running on your microcontroller, sends commands to, and collects reports from.
Achieving a blinking LED is a good start for working out the mechanics of getting code compiled, downloaded into your microcontroller, and running, but I would really rather that tutorials took it a step further and got the LED blinking under control of interrupt service routines triggered by hardware timer events. That is where you need to get to actually start doing real-world embedded-system programming.
So I am guessing that it is a firmware system preloaded and running on microcontrollers built into robot hardware that your own code, running on your microcontroller, sends commands to, and collects reports from.
Achieving a blinking LED is a good start for working out the mechanics of getting code compiled, downloaded into your microcontroller, and running, but I would really rather that tutorials took it a step further and got the LED blinking under control of interrupt service routines triggered by hardware timer events. That is where you need to get to actually start doing real-world embedded-system programming.