Part: Part Four - Pot Odds & Hand Analysis

Fold equity in a shove

Pre-flop
Blinds 100 / 200Pot 1,100 (5.5 BB)BB9♠8♠● 5,000 (25 BB)YOU25 BB stackBTN● 5,000 (25 BB)Buttonraises 500 (2.5 BB)SBfoldsD

You have a 25 BB stack in the big blind. A button player opens to 500 and you call with 9♠8♠.

25 BB deep, button opens to 500 (2.5 BB); you hold 9♠8♠ in the BB. Best?

WhyCall. With 25 BB a suited connector is fine to see a flop - and if you flop a draw, your short stack makes a powerful semi-bluff shove available.
What happensYou call. Heads-up to the flop with ~4,500 behind.  Pot: 1,100 (5.5 BB).
Flop
Heads-upPot 1,100 (5.5 BB)K♠6♠2♦BB9♠8♠● 5,000 (25 BB)YOUflush draw (9 outs), 22 BB behindBTN● 5,000 (25 BB)Buttonbets 600 (3 BB)D

Flop: K♠ 6♠ 2♦ - you flop a flush draw. He bets 600, and you have about 4,500 behind.

A check-raise all-in here is profitable mainly because of…

WhyFold equity plus draw equity. Calling realizes only your ~19% next-card equity. Shoving adds fold equity: he must fold every hand that can't continue, so you often win immediately - and when he does call, you still have ~35% to make the flush by the river. The two together make the semi-bluff all-in clearly +EV.
What happensYou check-raise all-in for 4,500; he folds a middling king.  You win without a showdown.
With a draw and a short stack, the shove beat the call because it added fold equity to your draw equity - you won the pot outright a good share of the time, and still had ~35% on the times you were called.

A semi-bluff all-in is powered by two things at once - the chance he folds now, plus your equity when called; together they can make a shove +EV that a passive call is not.