Ethereum can be mined, while Ripple cannot be mined. (Ethereum does not have a supply cap as of this writing whereas Ripple is finite and has a total supply of 100,000,000,000)
Ethereum is a blockchain which decentralized apps can adopt or build on. Ripple is similar to a software which can be adopted by banks or financial insitutions to carry out transactions.
Each Ethereum transaction costs ‘Gas’ that goes to the miners that complete or confirm your transactions. Whereas Ripple gets destroyed after every transaction.