A Plunko Board is necessary to Prestige. Prestige is the "Soft Reset" in Turbo Town.
To prestige you need to build a Plunko Board and assign 76 cubies to it. When you prestige, Mr. Business shows and drops every building of your town onto the board. Every building scores Plunko points according to it's Plunko value denoted in the building description multiplied by the slot value in which it lands (1x, 5x, 10x, 5x, 1x). Eg. if the building lands on 5x it's worth 5 times its normal value in Plunko points. The board can be tilted incase buildings get stuck.
According to the point amount, a number of briefcases is awarded. Angel Wings are also awarded and your angel buildings are refunded.
A new town in a new board is then created. You retain all your achievements, quests (incl. quest progression), boost items and bucks, but lose all coins and ressources.