Lisk allows developers to build decentralized applications (dApps) on their own “sidechains” of the main Lisk chain. This special feature is designed to increase the security of the network. Each smart contract developed on Lisk has its entire own chain. Bugs that can compromise the side chain would theoretically not be able to effect the main chain. Ethereum experienced a bug similar to the bugs Lisk aims to squash with DOA (Decentralized Autonomous Organization) in 2016.
Announced in 2016, Lisk has multiple differences then Ethereum. Starting with the foundation of the chain, Lisk uses Delegate Proof of Stake (DPoS) consensus algorithm verses Proof of Work (Ethereum currently uses) and Proof of Stake (Ethereum is transitioning to).