You're reading the documentation for a version of ROS 2 that has reached its EOL (end-of-life), and is no longer officially supported. If you want up-to-date information, please have a look at Iron.
Several advanced robot simulators can be used with ROS 2, such as Gazebo, Webots, etc. Unlike turtlesim, they provide fairly realistic results relying on physics-based models for robots, sensors, actuators and objects. Hence, what you observe in simulation is very close to what you will get when transferring your ROS 2 controllers to a real robot.
This set of tutorials will teach you how to configure different simulators with ROS 2.