Blockchain is a database that stores transactions, these transactions or the data stored can not be modified after the fact.
Linked computer systems verify blocks and each block contains a hash. It also contains the hash of the previous block to maintain integrity. A hash is a form of a coded message in which the data is encoded using numbers and letters. If any data within the block is altered the hash immediately changes and the nodes become aware that the data is not authentic. A change of a single letter in a word would trigger a hash change. Hashes have the same length, regardless of the amount of data. Changed hash breaks the chain and the computing power to keep the chain together with this fake hash would be too high.
Blockchain was derived from Bitcoin and has gained many institutional supporters. Banks have a unique interest in the technology in that they believe it has value in being integrated into the banking system.
Torgeir Storstrand, Tech Writer AIOIS