A DataNode is a component in a distributed computing system, particularly in frameworks like Hadoop. It is responsible for storing and managing data blocks, ensuring that data is available for processing. Each DataNode works in conjunction with a central server called the NameNode, which keeps track of where data is stored across the cluster. DataNodes communicate with the NameNode to report the status of the data they hold. They also handle read and write requests from clients, allowing for efficient data retrieval and storage. This architecture enhances data reliability and availability, making it suitable for large-scale data processing tasks.