What is a "Play-through"

Play-through is exactly the same concept as "wager requirement":it consist in a certain amount of bets/ hands to do before the players can be able to cashout the winnings.
But we ask: when play-through is satisfied and wager requirements reached, the bonus is cashable?
We don't have a general solution for this question. It's always better read and understand the casino terms and conditions about all concerning the bonus received.
But we know that: when a bunus is cashable, usually online casinos are proud to promote this aspect of bonus in advertising or in evidence in main casino site. If you can't found any informations on site and you must read the terms and conditions, maybe the bonus is not cashable.
Now it's better to explain how to cash out a bonus with an example.

Exemple: If you have received a 100% Match Bonus of $100 - you have deposited $100 and have a total of $200 in your bankroll to gamble with. If wager requirement are 20x, bonus + deposit amount, the full amount needed to be played through in the casino would be $200 x 20 = $8,000. Granted there are some online casinos that will allow players to cash out portions of the bonus as the wager requirement is steadily met. If you had reached the point of gambling $4,000 of your deposit and bonus money, you would be halfway to the point of meeting the entire wager requirement. Therefore, at a pro-rated value, you should be able to cash out half your bonus ($100) which some casinos will let you do, but at the cost of forfeiting the remainder of your bonus.

It's no deposit bonus cashable?

No. We don't know for now any online casinos that allow to cash out your no deposit bonus amount. If you grant the wager requirements you can cash our your winnings (but remember for no deposit bonus are some maximum limits for winnings without money). But the winning are decreased of value of original no deposit bonus received.