A Distributed Hash Table (DHT) is a distributed system that provides a decentralized key-value store. It is used in peer-to-peer (P2P) networks to store and retrieve information in a scalable and fault-tolerant manner.

In a DHT, each participating node stores a subset of the key-value pairs, and a mapping function is used to assign keys to nodes. This allows nodes to locate the value associated with a given key by querying only a small subset of nodes, typically those responsible for keys close to the given key in the mapping space.

DHTs provide several desirable properties, such as self-organization, fault-tolerance, load-balancing, and efficient routing. They are commonly used in P2P file sharing systems, content distribution networks, and distributed databases.

One popular DHT algorithm is the Chord protocol, which uses a ring-based topology and a consistent hashing function to assign keys to nodes. Another widely used DHT is the Kademlia protocol, which uses a binary tree-like structure to locate nodes responsible for a given key.