I don't understand this puzzle I solved

Hi

I don't understand this puzzle I solved.

I'm white, it shows black moves first Rh8 and then i/white am meant to continue.

I see two moves for white Bh5, Re8 and it says correct.

1. ... Rh8 2. Bh5 Kg8 3. Re8

and it says correct.
but I can't see a checkmate, i'd have thought he could do Kh7. But it won't let him it seems. I don't see why.

so, i'm not seeing what this puzzle is getting at.

I can't continue playing it in my head.  I don't know how I am meant to work out why these were even such good moves.  I can't see where there are good exchanges or a checkmate. 

edit- forgot link https://www.chess.com/puzzles/problem/122793 

I don't do the puzzles on a regular basis, so I'm not familiar with the puzzles here. I'm assuming you're talking about this one: https://www.chess.com/puzzles/problem/122793

I also assume that Black will play 1. ... Rh8 as you stated.

As far as I can tell, this is *not* a quick mate problem. In fact, it's only a gain of material, and not too easy to see, at that. Yep, the line continues 2. Bxh5+ Kg8 3. Re8+ Kh7.

Now here's where it gets interesting: Your best move here is 4. Bg6+ (which at first glance seems stupid.) The line continues 4. Bg6+ Kxh6 5. Rxh8 Kxg6. So, you're giving up two bishops for a rook, which seems like a bad trade. However, your followup is 6. Rc8! Now, regardless of what Black does, he'll lose either his knight or bishop. For example, 6...Bb7 7. Rc7, and now one of Black's pieces will fall, and the combination ends up being a gain in material for you. (You finish being up an exchange, not including the pawn you snagged at the very beginning.)

Not easy to see for a relative beginner...The puzzle states that the puzzle rating is 235. Does that mean 235 elo, or something else? This is *NOT* a beginner puzzle...

Well, I take back my last statement about this not being a beginner puzzle, if you look at it as a quick way to gain a pawn without losing any material. Whatever. :-)

I just picked analysis and tried playing out what you said. "7. Rc7, and now one of Black's pieces will fall,"

RC7 by me/white is bad, because the knight can take the rook.

You moved the rook to b8. Move it to c7 instead. :-)