I need help with dialog constructor

This is my first C++ project, I'm learning C++ by writing code.
I am using Code::Blocks 13.12 running on Linux Mint 17.3 with the Mate desktop.
It's a wxWidgets project.

When I run the program I get the xwWidgets Application Template dialog instead of the one I made.
The problem appears to be here, it's autogenerated code from Code::Blocks.
 
  UserDialog* dlg = new UserDialog(0L, _("wxWidgets Application Template"));

Specifically the "_("wxWidgets Application Template")"
I've wasted several hours looking for an explanation of the constructor.
Should I use UserDialog.cpp where wxWidgets etc is?
I would greatly appreciate a full explanation of this, or a reference with examples.
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