What is Block chain ?
In simple words if you ask ,I would say ,
“Block chain is decentralized database with strong consistency support.”
A decentralized computation and information sharing platform that enables multiple authoritative domain,who don’t trust each other ,to cooperate, coordinate and collaborate in rational decision making process.
So blockchain broadly you can think of it as a decentralised database which helps in cooperation between multiple authoritative domain. So, the technology is particularly useful when multiple parties or individual they want to cooperate it with each other, and they want to come to a common platform to share the information among themselves.
Blockchain is Bitcoing ?
No ,Bitcoin is first production release application which was formed on blockchain technology.
Please see below video to understand more .
How Does it work ?
So It begins with someone doing a single or a group of transactions. A transaction is typically sending data in the form of a contract.
Depending on the blockchain implementation you are using, it can also involve crypto currency being sent from one account to another. The transactions are sent to a large peer to peer network of computers. These are generally distributed all over the world.
Each computer is called a node and they all have a copy of the existing data. Then the transaction is executed and validated based on pre-shared contracts and scripts. This ensures that all nodes execute using the same set of rules. When the transaction has executed, the result is added to the blockchain. Since this is done at each node, you would have to compromise every node in the chain in order to compromise the transaction.