Proof of Work (PoW)
In cryptography, the proof-of-work protocol or PoW is a protocol used to prevent cyber attacks such as DDOS and spam. It emerged as an attempt to reduce the effects of these attacks using hash functions. For a user to perform some action, he must be able to prove that he performed some task, this proof is the guarantee that the user spent time to generate an answer that satisfies some requirement of the evaluator. For this system to work, such evidence must be laborious to create, but easily verified by the evaluator. Its initial use was in electronic correspondence, but it was eventually applied to cryptocurrencies such as Bitcoin to verify transactions, ensure blockchain consensus, and mine coins. Proof of Stake (PoS)