Proof of Stake (PoS) is a consensus mechanism used in blockchain networks to validate transactions and secure the network. PoS selects validators based on the amount of cryptocurrency they "stake" or lock up as collateral. The more cryptocurrency a user stakes, the higher their chances of being chosen to validate new transactions and add blocks to the blockchain.
In PoS, validators are rewarded with transaction fees or new coins for their participation. This system is considered more energy-efficient than Proof of Work (PoW), because it eliminates the need for energy-intensive mining. In addition, PoS encourages long-term investment, due to validators having a vested interest in the network’s success. However, PoS has its challenges, such as the potential for wealth concentration, where users with more staked coins have more influence over the network.