Users who want to lend their currency at a fixed interest rate can buy fCash. A lender exchanges their currency at the time of trade for a greater, fixed amount of that currency at a specific point in the future. The exchange rate that the user gets implies a fixed interest rate on their loan between the moment they trade and the time that their fCash matures.
In the following example, a lender loans 100 DAI to the liquidity pool at an fixed interest rate of 5% for 3 months. When the loan matures on December 1, 2020, the 100 DAI loan plus the 5 DAI fixed interest rate is returned to the lender.
When the loan matures, the lender can redeem their fCash for currency.