There are two types of boosters. Dress boosters and other boosters. Dress boosters are associated with the specific dress worn in the match 3. Collect enough gems of that color and a booster will automatically be placed on the board to help you.

There are four other boosters that sit either side of the dress booster, at the bottom of the screen. You can tap on these whenever you like, to help you out. These boosters can be purchased with currency or earned through daily rewards and the free gift box that appears in the shop.