How Does the Blockchain Work ?
Each transaction is a digital ‘block’ that needs to be verified before it’s allowed to enter the system. Questions include: Is the money there? Are sender and receiver reputable? Is the request legitimate? And so forth. Each computer on the network competes on unscrambling the answers, and the winning computer adds this ‘block’ to the ‘blockchain’ in the order that the ‘block’ arrived. The winner broadcasts his proof to the rest of the network, which checks that proof and verifies it before queuing the ‘block’ to complete the transaction. Parties involved are assured that participants have screened and okayed the transaction.
The process not only cuts down on fraud, such as double spending or spams, but also transfers funds simply, safely, and fast.
Excerpt and image source : http://blockgeeks.com/guides/blockchain-applications/?ref=quuu