Paxos is a consensus algorithm used in distributed systems to ensure that multiple nodes agree on a single value, even in the presence of failures. It was introduced in a 1978 paper by Leslie Lamport and is designed to achieve reliability and consistency in environments where network partitions or node failures can occur. The algorithm operates in three main roles: proposers, acceptors, and learners. Proposers suggest values, acceptors vote on these values, and learners learn the chosen value once a majority of acceptors agree. Paxos is foundational for many modern distributed systems, including databases and cloud services, ensuring they function correctly despite potential issues.