There are four tokens, Spring, Summer, Autumn, and Winter. They've been designed to rise in price relative to each other in a predictable sequence. Spring tokens will tend to rise in price, then Summer, Autumn, Winter, and Spring again.
The prices of the tokens relative to each other are driven by supply and demand. There's a supply from mining, and a demand from farming. Once every nine months, the rate of production of a token halves, and the cost of production doubles. It goes from being the cheapest to produce, to being the most expensive. Then it goes from being the least valuable for farming, to being the most valuable.
This combination of seasonal supply and seasonal demand provides the pressure on the prices of the tokens relative to each other that makes them increase in a predictable sequence. If you trade the tokens in a cycle, you'll end up with more than you started with.
The tokens have been designed so that there's always a difference between the way that the market currently prices them relative to one another and their long-term value. One token will be the most expensive, and another token will be the cheapest. Investors can increase the total number of tokens they own by trading the more expensive tokens for the cheaper ones.
If you always trade tokens for more tokens of a different type, the total number of tokens in your investment will increase with every trade. In the long term, the tokens are equally valuable, because which one is the most expensive will keep rotating.