Docker Swarm is a container orchestration tool that enables you to manage a cluster of Docker nodes as a single virtual system. It allows you to create and maintain a pool of Docker hosts, and deploy and manage services on those hosts.
For example, you can use Docker Swarm to deploy a web application across a cluster of servers. You can define a service that runs on each node, and configure the service to scale up or down as needed. You can also use Docker Swarm to quickly roll out updates to your application, or to add new nodes to the cluster.