C++ : Default constructor defined with default arguments outside the class definition, why does this

C++ : Default constructor defined with default arguments outside the class definition, why does this work? and what happens with templates involved?
To Access My Live Chat Page,
On Google, Search for "hows tech developer connect"

I promised to share a hidden feature with you, and here it is.
This is a YouTube's feature which works on Desktop.
First, Make sure this video is playing.
Then, type the letters 'awesome' on your keyboard as the next step.
Your YouTube progress indicator will turn into a shimmering rainbow.

A brief introduction of myself,
Hi there, I go by the name of Delphi.
I am willing to help you find the solutions to your questions.
C++ : Default constructor defined with default arguments outside the class definition, why does this work? and what happens with templates involved?
If you require more detailed information, please don't hesitate to comment or chat with me.
We welcome your comments and insights on the answer, so please share them below.
Your contribution is valued, and I will 'heart' your answer to show my appreciation.
defined and : arguments does Default happens work? why with C++ constructor class this the what outside templates with involved? default definition,