I dont understand Part III of the rosject

The Part III of the rosject states that I should create an action server that records odometry data and modify the existing client node so it calls the action server before calling the service server. When the service server is running, it can’t do other things in the meantime. So, am I to make the robot record odometry data and move at the same time? or am I to make the action server and service run simultaneously? Please I need a clarification on what I am to do for the Part III of the rosject.

First, you should call the action server to start recording odometry data. As mentioned in the course, you can run other nodes while running your action. so, after you run the action server and action client, you can run your service server and call it. as a result, your action and service will run simultaneously.

you can also first start the action server and service server, then call them by action client and service client in order.

I hope this helps.