What is a blockchain?

It would seem, so not clear words few years ago, now become a mainstream.

What the animal this "blockchain" and whether he will replace a real financial system is.

What is a blockchain?
It is one of types decentralized data storage in which chains of blocks are used.
It can be compared to the diary in which each line is the block, and the diary to be stored and is supported by a large number of computers.

Why such happiness is necessary for us?

To store story of changes of the database with absolute transparency.
How to use?

Here present, a certain Vasya owes you $1000. You of course on friendship haven't taken the receipt or, as always, have taken, but have forgotten where, have put, well and you have no witnesses too. After a while Vaska was drawn. Also I have told that all this nonsense, and you everything has dreamed. As a result, you were left high and dry, and Vasya with your money. In this case need of a blockchain so bike. Millions of blocks will testify yours transactions. With Vasek, your friend, won't suffer amnesia.

For record
I am not sure whether the blockchain will replace a real financial system, but for certain will replace that it is necessary for each of us: confidentiality, transparency and accuracy.