Is the 'x' in ConstPtr& x in callback functions specific to message types?

edit

Hi I'm new to ROS and I'm an amateur when it comes to pointers. I just did the subscriber and publisher tutorials and I am currently experimenting and converting them into classes for future use. I noticed that in the callback function it has the following parameters:

 void chatterCallback(const std_msgs::String::ConstPtr& msg)

then I opened another cpp code with a subscriber and found:

  void joyCallback(const sensor_msgs::Joy::ConstPtr& joy);

My question, is 'joy' and 'msg' specifc to use for their message::message type? How can I know what to put after the ConstPtr& say for sensor_msgs::Range? Thank you.