Proof of Authority (PoA)

A private key that gives the holder the right to create the blocks in a private blockchain. It can be held by a single entity or a set number of entities. This is an alternative to the proof-of-work model, as instead of getting multiple random nodes to approve a transaction, a group of specific nodes are given the authority to approve. This is a far faster method.

Proof of Stake (PoS)

Another alternative to proof of work, this caps the reward given to miners for providing their computational power to the network at that miner’s investment in the cryptocurrency. So if a miner holds three coins, they can only earn three coins. The system encourages miners to stick with a certain blockchain rather than converting their rewards to an alternate cryptocurrency.

Proof of Use (PoU)

Proof of Use (PoU) is when a cryptocurrency is used to buy goods and service or barter for goods and services and is not traded as a speculative coin for someone to buy low and sell high but used as a form of currency and leverage.

Proof of Work (PoW)

In order to receive a reward for mining a cryptocurrency, miners must show that their computers contributed effort to approve a transaction. A variable is added to the process of hashing a transaction that demands that effort before a block can be successfully hashed. Having a hashed block proves the miner did work and deserves a reward – hence proof of work.