At the core of Fluidity lies Fluid Assets, which pay yield when you use them.
A Fluid Asset is a wrapped standard (ERC-20, SPL) token that represents an underlying principal token.
A novel property of Fluid Assets is that they expose users to randomly paid rewards or yield when they are used (sent or received).
For example, one Fluid USDC (ƒUSDC) would simply be a USDC token deposited into the Fluidity Protocol. It is worth the same as the underlying principal and can always be redeemed for the underlying collateral.
A Fluid Asset is different than a yield-bearing asset. A yield-bearing asset such as cUSDC or aUSDC would pay yield when you hold onto it, whereas a Fluid Asset pays yield when you use it.
This creates an incentive to utilise your cryptocurrencies instead of holding on to them.