In this paper we are going to go through blockchain technologies. No matter which blockchain you're developing on blockchain engineers are in extreme demand. Protocols like Aave, Yearn Finance and Synthetix have huge sums of monetary value locked in them allowing people to engage in decentralized finance (DeFi), which allows people to make censorship resistant moves. Some of these protocols are less than a year old. Blockchain and solidity applications are building a world of more trust and accountability with smart contract engineering skills becoming the most sought after in the world.