This term refers to a collection of computer files that store transaction data. They are arranged in a linear sequence, forming an endless chain of connected blocks. It refers to a term of blockchain.
All information regarding blockchain transactions for a certain time period is collected and recorded in the form of such block, and each subsequent generated block is connected with the previous one by methods of cryptography.
Each chain stores all transaction data created since the launch of each specific blockchain. With access to the chain, you can get to the first block, which is also called the “zero” or “genesis block”. Also, the ""block height"" means the amount of confirmed subsequent blocks, starting from the first one.
As an example, we can take the structure of the ""Bitcoin blockchain"" block. In addition to basic information, each of them contains a list of recent transactions, timestamps, and a link to the block that appeared before it. This link is a cryptographic data hash of the previous block.
During the generation of a new block, the hash of the previous block is taken as the basis, which makes them cryptographically connected. This hash acts as an identifier. It is unique for each individual block and created through a process known as mining. The resulting chain of cryptographically related blocks is a complete database, which is also have increased resistance for hacking.
Creating a hash is a solution to a complex mathematical problem and the miner who resolves it gets the right to check the received block and the transactions which it contains. Also because the mining process requires large computing resources, miner receives bitcoins from a freshly generated block as a reward.
There might be situations when two or more independent miners find the hash of a new block almost at the same time. And the chain is embedded by two blocks, which leads to the formation of two competing branches. This problem can be solved by the next way - other network participants (nodes) are choosing which section of the chain to build further by themselves.
And the chain which becomes longer will contain a lot of “accumulated work” or transaction data, which will be a logical continuation. The second branch will be discarded, and the blocks in it will be considered as ""obsolete"".
The blocks are mostly discussed in the context of cryptocurrency transactions, but they also can contain other digital data since the blockchain system can be used for other purposes.