The higher your tier, the more benfits you'll unlock! Plant Powered Rewards members have 3 different tiers: Gold, Platinum, and Diamond. When you sign up, you'll automatically start in the Gold tier. You'll be able to level up to the next tier once you spend and earn a certain point threshold.
Everybody starts in Gold once they create a No Cow account, while Platinum ($200+ spend), and Diamond ($500+ spend) require certain spend amounts to reach. With each tier, you'll also unlock new benefits and redemption opportunities, all the while being able to claim discounts on future nocow.com orders.