How can i use rviz to simulate my own robot-model [closed]

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Hi community l am new to ros ,i have done many tutorials and read the book about ros ,e.x. ROS By Example.In that book,i do the example use Arbotix simulator step by step.But i can't understand what happened behind screen.i want to do something use my own robot-model in rviz.i have built up my robot in urdf . But i don't know what should i do the next.please see my questions below :

1.how to drive the model built by urdf in rviz

2.if any tutorial exists in ros.org

3.the different between rviz and gazebo ....

my English is not very well ....

i wish i have described my questions clear .

thanks everyone