The verification and cryptographic sealing mechanism that is critical to the bitcoin network involves a computationally intensive process. A large number of nodes in the bitcoin network engage in the verification process.
The process provides a mechanism that avoids false duplications of voters and forces voters to demonstrate computational capacity. To secure a qualified majority, the system employs a cryptographic sealing process that is computationally intensive. The process includes a challenge called “proof of work.” The first node that solves this challenge receives a bitcoin reward. This mechanism, called “mining,” enables new bitcoins to be created.
https://www.cryptocoinsnews.com/bitcoin-mining-costs-large-fair/