diff --git a/gh_pages/_source/session1/ros2/3-Creating-a-ROS-Package-and-Node.md b/gh_pages/_source/session1/ros2/3-Creating-a-ROS-Package-and-Node.md
index 8dcb48f0f..70ffc075a 100644
--- a/gh_pages/_source/session1/ros2/3-Creating-a-ROS-Package-and-Node.md
+++ b/gh_pages/_source/session1/ros2/3-Creating-a-ROS-Package-and-Node.md
@@ -134,6 +134,8 @@ Your goal is to create your first ROS node:
    * To use a different logging level, replace INFO in `RCLCPP_INFO` or `RCLCPP_INFO_STREAM` with the appropriate level.
    * Use `RCLCPP_INFO` for printf-style logging, and `RCLCPP_INFO_STREAM` for cout-style logging.
 
+   `rclcpp::spin(node)` instructs the node to listen for any activity on subscribed topics or requested service connections. Without it, your callback functions won't ever run. Don't worry if some of this language doesn't yet make sense, we'll cover topics and services in the next sections. (More technical details [here](https://docs.ros.org/en/rolling/Concepts/About-Executors.html).)
+
 1. Now that you have created the source code for the node, we need to add instructions for building it into an executable program. In the package folder, edit the _CMakeLists.txt_ file using _gedit_. Define an executable node named vision_node (_add_executable_), with the source file _vision_node.cpp_. Also within the _CMakeLists.txt_, make sure your new vision_node gets linked to the required dependencies.
 
    ``` cmake