How to define odom topic for a robot?

In the ROS control course, it is explained how to create and set controllers for joints.
my question is, how to create an Odom topic for our robot (real and in the Gazebo)? What are the steps?

Hello @m.haghbeigi ,

For a real robot, odometry is usually computed from the wheel encoders. You can see an example of this in the Basic Kinematics of Mobile Robots course, Unit 3 (Kinematics of Nonholonomic robots). Here you can access the course: Learn Robotics from Zero - Robotics & ROS Online Courses

For Gazebo it is normally used the differential drive plugin (which does all the calculations for you). You can check this video to see how to configure it: [ROS Q&A] 126 - How to configure the differential drive ROS controller - The Construct