wow!
The Starter (And the first daily puzzle ever made!)

@travisignash
In the top one 2.Qxc3 the pawn is undefended so can be captured. It also blocks any other queen checks on the a1 to h8 diagonal.
In the bottom one the pawn on b2 defends c3 so can't be captured.
Cool Easter egg (?) for the first ever puzzle!

It looks like this puzzle has changed a bit.
I was curious when this first puzzle appeared. It was 8 May 2007.
https://www.chess.com/daily-chess-puzzle/2007-05-08.
This was the first daily puzzle on Chess.com. It was called unstoppable mate, but it actually had a major flaw, which made it so that the mate was not unstoppable!
Flawed Version (Try the Edited puzzle beforehand)
In this puzzle, if black played 2.Qxc3, there would be no checkmate at all!
The creator of this puzzle meant to put a pawn on b2.
Edited Puzzle (Try this one)