X-rays are a form of high-energy electromagnetic radiation, with wavelengths shorter than those of ultraviolet rays and longer than those of gamma rays – roughly in the range of 0.01 to 10 nanometres. X-rays were discovered by German scientist Wilhelm Röntgen in 1895, who named them X-radiation to signify an unknown type of radiation. X-rays can penetrate many solid substances such as construction materials and living tissue, and X-ray radiography is widely used in medical diagnostics. This medical significance was noticed by Röntgen shortly after he discovered X-rays; this print, titled Hand mit Ringen (Hand with Rings), is a print of his first medical X-ray, taken of his wife Anna Bertha Ludwig's hand in December 1895.Print credit: Wilhelm Röntgen; restored by Yann Forget
Special:MyPage is a special link that is dynamically linked to the current user's userpage. So, whoever clicks on it will be taken to their own user page.
If you add a subpage to the link, then only you will be taken to your subpage of that name. Other users will be taken to the subpage of that name in their namespace (if it exists).
This makes the link "private" by only letting the correct user get to the page via that link. Other users will diverted to their own userspace.
The code [[Special:MyPage/To-do list|To-do list]] creates this: To-do list.
However, this only makes the link private, not the page itself. Others can still get to it via the search box or by creating a new link with its entire title.