Yes it is defined as the Profile page,
If you click on Profie in your own User mene at the top of this page you see moodle.org/my
yet I see this...
https://moodle.org/user/view.php?id=26675&course=5
If you enable the Debugging setting to "Show page info" in footer, you will see the layout optioned defined for that page and is refered to as "mypublic"
Site Administration > Development > Debugging
debugpageinfo Default: No Enable if you want page information printed in page footer.
It's good to have that setting on when trolling about your own site while working on it, as you see the many page layouts visited while performing a task. For instance the calendar uses various layouts from Admin which is a two column layout to Standard which is a three column layout, and yet the calendar needs lots of space. Therefore you need to know which layouts your site uses most to determine how to style theme for the look you are after.
Mary