An Ethereum client refers to any node which can parse and verify the Ethereum blockchain and execute smart contracts on top of it. As we have seen in the early sections of this chapter, the main purpose of user-faced clients is to authorize user credentials and provide an interface to conduct various operations. They also provide interfaces to create transactions and mine blocks, which is crucial for blockchain interaction. Figure 2.16 illustrates the classification of Ethereum client interfaces:

A wallet provides a service of sending, storing, and receiving funds. The main parameters of a good wallet service are security and trust. Users must feel that their funds are secure and the administrator of the wallet will not steal the funds. Such wallets are known as hot wallets, because...