Connect ROS with Gazebo beginner tutorial

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I'm new in ROS and Gazebo.

I'm studying robotics at the university and I need to move a robot in Gazebo using ROS. I will control the robot with the keyboard.

My problem is that I have no idea about ROS or Gazebo. I did the ROS' beginner tutorials and also some tutorials from Gazebo (the ones that talk about gazebo plugins).

I've stated reading the Gazebo: connect to ROS tutorials, but it is a mess. They talk a lot of things that I don't understand. To be more specific (the tutorials are here, http://gazebosim.org/tutorials?cat=co... ):

1. In Using a URDF in Gazebo, they talk to convert URDF files to Gazebo. Do I need to do that?
2. In Using Gazebo plugins with ROS, I found a question about writing a Gazebo plugin to handle a robot in Gazebo, and someone answered that we can do that using ROS. Do I need to write Gazebo plugins to connect ROS with Gazebo?
3. In ROS Control, they explain how to add transmission elements to a URDF. If I modify the URDF to use it with Gazebo, will I still using it in a ROS package?
4. I get tired to read and don't understand anything. I decided to ask here.

Reading that I think that those tutorials are for advanced users because they do thinks that I haven't do yet. I haven't modify a SDF file, I use the Gazebo's editor to modify the robot or the world.

I just need a tutorial to follow that talks about how to connect gazebo with ROS, add a robot and control it with a keyboard from ROS.

Do you know if there is something like that?