Webots (https://cyberbotics.com) is a simulation environment for the design and modelling of robotic systems. Since robotics invariably results in some physical actuation, Webots can also be used to model Cyber-Physical Systems, and being open source, the software is free to use and experiment with.
Webots is particularly suited to newcomers to robotic systems, though it can still be used more formally in industrial scenarios, via links to the Robot Operating System (ROS – https://www.ros.org).
If you have a need to develop a robot, a physical control of a process, or you are just curious, Webots is a good place to start.
I use Webots for teaching both robotic systems and cyber-physical systems, usually in the context of digital manufacturing/Industry 4.0. You can model entire systems at an abstract level, or focus on the detail of sensors interacting with each other.
Some more reasons to use Webots can be found here: https://cyberbotics.com/#webots
To get a working installation of Webots, you should visit the excellent documentation that is located at: https://cyberbotics.com/doc/guide/installation-procedure#installation-on-macos