Ethereum is a decentralized platform, which allows us to deploy DApps on top of it. Smart contracts are written using the solidity programming language. DApps are created using one or more smart contracts. Smart contracts are programs that run exactly as programmed without any possibility of downtime, censorship, fraud, or third party interface. In Ethereum, smart contracts can be written in several programming languages, including Solidity, LLL, and Serpent. Solidity is the most popular of those languages. Ethereum has an internal currency called ether. To deploy smart contracts or to call their methods, we need ether. There can be multiple instances of a smart contract just like any other DApp, and each instance is identified by its unique address. Both user accounts and smart contracts can hold ether.
Ethereum uses blockchain data structure and proof-of-work consensus protocol. A method of a smart contract can be invoked via a transaction or via another method. There...