A centralized blockchain is a blockchain where a specific entity controls all nodes. This entity can be a single organization or a consortium of organizations. A decentralized blockchain is a blockchain that any individual or organization does not control. Instead, it is maintained by a network of computers that all have a copy of the blockchain. This makes it difficult for anyone or an organization to tamper with the blockchain. Centralized blockchains have several advantages over decentralized blockchains. First, they can be much faster, as there is no need to wait for consensus among all of the nodes in the network. Second, they are more secure, as there is only one point of failure. Third, they are easier to use, as there is no need to install and configure a blockchain client. However, centralized blockchains also have several disadvantages. First, they are less decentralized and thus less trustable. Second, they are more vulnerable to attack, as hackers can target the central authority. Third, they are less scalable, as the number of transactions that can be processed at once is limited by the bandwidth and CPU power of the central authority's nodes.