An agent is the CloudBees CI component that connects to a Jenkins controller and executes tasks as directed by the controller. It can be installed on a computer, virtual machine, or container. You can configure an agent to have multiple executors, meaning it can run multiple tasks at a time for the controller that it is connected to. In CloudBees CI, an agent can be a shared resource available to multiple controllers or it can be dedicated to a single controller.
See also shared agent.