Triple Town's "Boom Town" map is a timed version of the standard Triple Town gameplay. It is currently available in the mobile game only, on version 1.54 and higher.
You access Boom Town from the "Select a map" screen:
People who have purchased Unlimited Turns can play as much Boom Town as they want whenever they want. People who have not purchased unlimited turns may have to watch a video or wait a certain amount of time between Boom Town games (but you are never forced to pay to play or forced to watch ads to play):
Prior to the start of the game, you have the option of unlocking one or more boosts in exchange for coins. You don't have to do this, but you can if you want to.
After you've chosen which boosts you want, click the Play button. You now play Triple Town as normal, but on a 2-minute timer. There are no Ninjas and no Grass, and you might be given Houses or Mansions to place. There are also 5 Crates on the board that contain Crystals--if you want to play a Crystal, click on a Crate to get one.
Also, each piece that you place is affected by a multiplier prior to the points being added to your score. You can learn more about multipliers by clicking here.
Assuming you survive to the end of the 2 minutes, at the end of the game the structures on the board are awarded points a second time. You are then awarded coins depending on how you scored relative to your previous Boom Town scores--you get more coins if you beat your previous high scores. (However, if you do not survive to the end of the 2 minutes, you are awarded only 5 coins regardless of how well you performed.)