Chainlink is a decentralised system that aims to link smart contracts with real-world data. Since the blockchain is not able to access data outside its network, the developers of Chainlink want to offer a solution to this very problem. The system uses data from external sources to manage the execution of smart contracts when predefined conditions are met. Cryptography can be used to guarantee secure data flows and facilitate the operation of blockchains. Chainlink's solution: the user requests the data he is looking for from the nodes, which provide the requested data or response. The user then selects the version that is most convenient for him, at the lowest cost. The requested data is provided by several parties, thus encouraging them to be trustworthy. Chainlink has countless potential uses. For example, in the case of securities: data on market prices or interest rates are needed. Payments are made to a real bank account, which can be done via Chainlink. Insurance payments also require information from external sources, for example whether the aircraft for which the insured person has insurance has arrived on time, i.e. whether the payment request is real. In the performance of commercial contracts, GPS data on shipments, the supply chain system, customs information on the goods to be shipped are usually needed. All the necessary data can be added to the smart contract using Chainlink.