Blockchains and Sidechains
Bitcoin in its original, unmodified state has enormous utility. When it was created, the original designer(s) could not account for everything that would transpire after its launch. There are many aspects of the software that are final and unalterable. The consequences of final variables of Bitcoin results in a hard forks. In the occurance of a hard fork, the nodes running modified software sacrifice their ability to interact with the nodes running the original software. The altered nodes begin creating blocks differently and within six blocks there are two block chains - the original and the forked chain.