One doubt regarding starting urdf simulation gazebo in local machine?

In unit 3 of URDF the section where launch file to launch urdf in gazebo is explained , there is statement as shown below

This first launch spawns the given URDF file into the given point in space, if a gazebo simulation is running.
    You can call this first launch through a second launch, passing the necessary arguments to it

so it means if i have to use this launch file in spawning a urdf in gazebo in my local machine i have start Gazebo before hand ?

If thats the case can i use this command to launch gazebo and the use the spawn.launch to spawn the urdf in gazebo in my local machine ?

roslaunch gazebo_ros empty_world.launch

Exactly. Although in the public repositories of the simulations you can find also launches for the MIRA or Gurdy simulations: MIRA world launch