Segwit is the short form of segragated witness. This is an advanced bitcoin protocol that helps to store data in blockchain in a despotic manner. Artificial Intelligence is used here and more and more amazing features will be invented in future hopefully.
SegWit has been deploying to the bitcoin blockchain to support the OFF-chain development process. There is a lot of proposal working at the off-chain scalability solution to the bitcoin but the best candidate and it will be tested in litecoin will be only lightning network. SegWit helps lightning network to be applied in the bitcoin and litecoin blockchain.