"Validators" (also known as "validation nodes") are responsible for validating on-chain transactions. When a transaction is successfully verified, the verifier adds the transaction to the distributed ledger.

Generally speaking, validators will receive token rewards as an incentive for their "verification work". Instead, validators who misbehave will be punished (usually by being temporarily or permanently banned from the system).

The number of validators varies from blockchain to blockchain. Additionally, the types of validators vary based on different consensus mechanisms. Here, we only introduce the validators in the two most common consensus mechanisms.

Verifiers in PoW consensus mechanism

In networks based on PoW consensus mechanism, such as Bitcoin, validators are called miners. They gain the power to verify transactions by solving complex computational problems. The rewards they receive are based on their "work."

What is PoW? How does the PoW consensus mechanism work? Please refer to the chapters "What is Consensus Mechanism" and "What is Proof of Work".

Verifier in PoS consensus mechanism

In networks based on PoS consensus mechanism, such as Solana, Ethereum 2.0, Avalanche, etc. , participants need to pledge a specific number of network native tokens to become a validator. Validators who correctly participate in the verification process will be rewarded. Detailed reward rules vary from network to network.

What is PoS? How does the PoS consensus mechanism work? Please refer to the chapters "What is Consensus Mechanism" and "What is Proof of Stake".

Node vs. Verifier

Nodes in the blockchain network are divided into three categories:

• Light node
• Full node
• Archive node

As the name suggests, light node only Download block headers, not entire blocks. This reduced requirement allows users to interact with blockchain networks without the need for powerful hardware or high bandwidth. However, light nodes do not participate in the consensus process, which means they cannot act as miners or validators.

On the other hand, full nodes actively participate in block verification and check all blocks and status. While full nodes theoretically store data for the entire blockchain, they typically cache only the most recent data for faster access. For example, Ethereum full nodes only keep the most recent 128 blocks.

Archive nodes have the same functions as full nodes, but also archive all historical status data. This feature allows people to directly query the state of the blockchain at a certain point in time without having to slowly deduce it from the current data. Although archival nodes can participate in block validation, they are not obligated to do so.

You may also be interested in the following:

• What is a block?
• What is a 51% attack?

(Thanks to skrbug for correcting this section)