There is much being said about Blockchain. It's a technology that was invented exclusively for BitCoin - an electronic currency. Many are pursuing ways to use the concepts in the context of other problem sets. Unfortunately, much of that work is either in a very early implementation stage or simply under consideration - little, if any, real work has been done to practically apply the technology.
Blockchain, or a "distributed ledger," is truly useful in a narrow set of operations. Specifically, Blockchain is terrific if what you want to achieve involves transactions. The distributed ledger records all transactions across a number of untrusted nodes (read computers) virtually simultaneously. Each related transaction, like specific currency exchanges, are grouped in one long "chain." If, for example, I wanted to track the financial path of a single dollar bill, the transaction history in the distributed ledger (Blockchain), would allow me to see all of the transactions where that dollar was involved. Importantly, however, the transaction details would not necessarily be visible - just the fact that the dollar was involved and transferred from one party to another. This information would be available through the ledger and allow me to ensure that person A transferred the dollar to person B. The question becomes, how do we translate this concept of transaction auditing to other kinds of operations?
Ultimately, the answer to this question is based on the industry and the operation type. In healthcare, for example, there may be some opportunity to use Blockchain to verify test result integrity - tests and the results could be transmitted from lab to physician to patient. A distributed ledger could be used to ensure that the results are not manipulated and the data (test results) stays private. Unfortunately, business needs like conditional test result access and test outcomes aren't solved by Blockchain; that part of the business problem still depends on existing authorization technology that would have to be added to the Blockchain solution. As a result, Blockchain only solves part of the challenge.
As with many new technologies, Blockchain has loads of potential. However, it won't be appropriate for every problem and there will be many who try to implement it for problems it's not well suited. Take a look at this article for more insight on Blockchain and some potential uses.
Blockchain is a term widely used to represent an entire new suite of technologies. There is substantial confusion around its definition because the technology is early-stage, and can be implemented in many ways depending on the objective.