What are effective stacks?

I'vew seen the term thrown around quite a bit and don't actually know what it means.

Lets say two players are in a pot heads up at $0.10/.25. One player has $10 and the other has $43, the effective stacks are $10 because that is the most any player can win or lose in the hand.

Ah, I can definitely find myself using this term a lot more... I usually just say so and so has a certain amount and the other person covers.

effective stacks is the cool way to say it