This paper describes the applications and products of decentralized finance and the blockchain technology on which the applications themselves are based. The initial part of the paper presents the history of the blockchain, what is actually a blockchain, and its structure and composition. After that, the first cryptocurrency is described, Bitcoin, which is actually the originator of the blockchain technology itself and the so-called "king" of the decentralized movement. Paper describes the mining process and how it maintains protocol security. Then, the paper describes Ethereum, the platform on which decentralized applications are developed. Smart contracts, decentralized applications and their use are also described. The second part of the paper describes the concept of decentralized finance (DeFi), what are they in general, what are their advantages and disadvantages and transparency of operations. After that, the paper lists "DeFi" products that are currently most used, why they are used and what their purpose is, and how they are used. The last part of the paper focuses on the fusion of blockchain and the public sector. Possible applications of blockchain in the public sector are presented, as well as examples of already existing blockchain pilot projects in foreign countries.