Finding the location of a ROS node

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As part of my ROS re-education, I have been experimenting with the TurtleSim. I understand that the following command:

rosrun turtlesim turtlesim_node

..means execute turtlesim_node located in the turtlesim package. But I execute roscd turtlesim and listing the contents of that package, I can't locate the turtlesim node. The tree structure is shown below:

/opt/ros/melodic/share/turtlesim$ tree
.
├── cmake
│   ├── turtlesimConfig.cmake
│   ├── turtlesimConfig-version.cmake
│   ├── turtlesim-msg-extras.cmake
│   └── turtlesim-msg-paths.cmake
├── images
│   ├── box-turtle.png
│   ├── diamondback.png
│   ├── electric.png
│   ├── fuerte.png
│   ├── groovy.png
│   ├── hydro.png
│   ├── hydro.svg
│   ├── indigo.png
│   ├── indigo.svg
│   ├── jade.png
│   ├── kinetic.png
│   ├── kinetic.svg
│   ├── lunar.png
│   ├── lunar.svg
│   ├── melodic.png
│   ├── palette.png
│   ├── robot-turtle.png
│   ├── sea-turtle.png
│   └── turtle.png
├── msg
│   ├── Color.msg
│   └── Pose.msg
├── package.xml
└── srv
    ├── Kill.srv
    ├── SetPen.srv
    ├── Spawn.srv
    ├── TeleportAbsolute.srv
    └── TeleportRelative.srv

Can anyone help me understand how to pinpoint and locate the turtlesim, or any target, node?