A block is a storage space that can store data.
Block chaining not only links blocks together like linked lists, but also provides a series of methods to manage these data, so it is a storage system.
There are many nodes in the block chain, each node holds all the data, so it is highly available.
Each central node can generate blocks and write data, so each point is a central node, or the block chain is centralization. In order to control the whole system, more than half of the nodes must be controlled to control the vote, so the system has no manager.
In summary, the block chain is actually a decentralized storage system with no administrator, centralization, and all nodes have all data. As long as you want, you can become a node in the block chain at any time and participate in the generation and writing of the block. Bitcoin is based on the electronic currency on this distributed storage.