The ZBWorker is the class used to create Zeebe Job workers. The detailed API documentation is available here.
Your Workflow Definitions contain tasks. A task has a task type.
When you create a workflow instance, the broker will create a job for a task. A job is a specific concrete instance of a task.
An ZBWorker subscribes to the gateway for jobs of a specific task type, and continually polls the gateway for available jobs. When there is work for the worker to do, the gateway responds to the poll with a stream of jobs, and the worker's job handler is invoked for each job.