Googke sheet link:
https://docs.google.com/spreadsheets/d/1bk4AJBbEbEtfxNLENxyJQobtNL1I9OMAJfQQAfYwcUs/edit?usp=drivesdk

Here,
D1 is =XMATCH("*",A:A,2,-1)
C1 is =XMATCH("*?",A:A,2,-1)
B1 is =XMATCH("*?*",A:A,2,-1)

So B1 is the formula to get the last row of a column, I don’t understand the regular expression part of it.

I understand D1 gives 18 considering the empty string too(because * is greedy takes everything), I don’t understand the behaviour of B1 & C1 and the difference between both of them. I understand *? is non-greedy meaning will stop after 1st match.
Please help!