Here is a very quick and simplified explanation :
Bitcoins blockchain basically works as groups of decentralized systems working together to solve mathematical problems in the form of bitcoin transactions. When a system thinks it has solved a block or group or problems, the other systems check its work, and if 50% or more of the systems agree, the block is added to the blockchain. This is basically how the blockchain technology works, very simplified of course.
Very good explain for 4 line,thanks