First, let’s recap what Proof-of-Stake is.

Proof-of-Stake (POS) is a common blockchain consensus mechanism where users stake their tokens for the chance to add the next block to the chain. The network designates a validator (leader) who is responsible for proposing the next block. This is done through a pseudorandom selection process, influenced by the amount of cryptocurrency staked. Other validators vote on whether they agree with its contents, and when enough validators approve of it, the transactions contained within are permanently recorded on the blockchain.

The Algorand blockchain developed the Pure Proof-of-Stake (PPoS) to prevent any chance of centralization in the POS model. In PPOS, validators are randomly selected from the pool of ALGO holders. Since any ALGO holder can be chosen, the power isn't concentrated in the hands of only a few large stakeholders. This reduces the risk of huge security breaches and keeps the network more secure.

Just like POS, PPoS is more efficient and eco-friendly than Proof-of-Work (PoW), which requires miners to solve complex mathematical puzzles which require specialized equipment that use up a lot of electricity. With fewer barriers to entry, a network using PPoS is able to attract more validators, keeping the blockchain more decentralized and secure.