A block is part of the bitcoin network. Transactional data is permanently stored in a block. Also, the blocks are always sequential, and new data is added to the latest block. In simple words, it is a record book with a fixed size to it. Once a block is completed, a new block is generated, which is then attached to the chain of blocks. This is where the name of the “block” chain came. All the information in the block is encrypted and can only be accessed by the receiver and sender.