About the Block Chain

The definition of the Block Chain from the Wikipedia is :
" ... a decentralized and distributed digital ledger that is used to record transactions across many computers so that the record cannot be altered retroactively without the alteration of all subsequent blocks and the collusion of the network."
So the Block Chain technology creates a decentralized digital public record of transactions that is secure, anonymous, tamper-proof and unchangeable or, in other words, a shared Single Source of Truth (SSoT).

Some domains are already using it as a SSoT, i.e. :

This is the reason why we are now creating a Configuration Management Database (CMDB) based on the Block Chain technology, because a CMDB must be accurate, reliable as a Single Source of Truth.

With the arrival of the Internet Of Things (IoT), build an accurate and reliable CMDB will be a very difficult task since the tiny devices cannot afford to populate central databases to keep the CMDB updated. But with Block Chain technology, every device can afford to create a transaction on the distributed digital ledger in order to have the CMDB accurate.

Block Chain (two separated words) is different from Blockchain (one single capitalized word).

Block Chain is the concept behind Bitcoin, while Blockchain is a company, which provide a software and wallet that hosts a real-time browser of Bitcoin transactions.

As already explained by Anthony Wing Kosner on his excellent article about the Block Chain :

Block Chain, the concept, is even more important than Blockchain, the company. One way to understand why, is to consider one of the most ambitious projects related to Bitcoin, Ethereum. Ethereum is an open source platform for smart contracts built on top of Block Chain technology. It recently completed a $15-18 million round of crowd funding using its own value token, poetically called “ether.” Stephan Tual, CCO of Ethereum, describes block chain technology as “a method by which trust can be reached on an open network.” Bitcoin is the first and best know use case, but Ethereum, says Tual, “makes this technology applicable to just about anything else.”