Proof of Work
From Open Risk Manual
Definition
Proof-of-Work. It is a consensus algorithm that uses work as a scarce resource. In the case of the Bitcoin, this means computational power and the proof is in the form of solving a hash puzzle. The nodes compete in solving this puzzle by finding a specific number, the nonce, so that when one concatenates the block header and use the hash function on it, the value of the hash falls within a certain range.
