On Cointiply you earn Coins. Those Coins are tied to the U.S. dollar.
More specifically, 10,000 Coins = US$1.00.
The number of satoshis your Coins are worth goes up when the price of Bitcoin goes down. The number of satoshis your Coins are worth goes down when the price of Bitcoin rises. It stays constant in dollars, however.
We explain this in the following articles:
Why does the value of my Coins change?