ROS topics

Your turtle simulation node runs with the turtle as static. If you want to move your turtle using the keyboard, you need to have a node that will execute the operation of keyboard. There is a node in the system named turtle_teleop_key. Now you need to make this node communicate with the turtle_sim node as you expect to move the turtle with keystrokes. This communication is done over topic. Turtle_teleop_key node publishes messages to a topic which is subscribed by turtle_sim node. You need to use rosrun command to make the node communication

$ rosrun turtlesim turtle_teleop_key

Using rqt graph you can see which topic is making the communication between the nodes, for this you should command 

$ rosrun rqt_graph rqt_graph