Notification plugins determine what Rundeck does when a Job Execution starts or finishes, with either success or failure. For a general explanation on how job notifications work, see Creating jobs#Job Notifications
The Workflow Strategy determines how the steps are processed within a Job’s Workflow.
An Orchestrator plugin can determine how to use the Nodes selected by your Job Filter. By default, all of the filtered nodes will be used, in the order specified in your Job definition.
However an Orchestrator plugin can choose which of the nodes should be used, and when. For example, to limit concurrent execution to a subset of the nodes, or to skip certain nodes.
Log Filters can filter/process/read output from specific Workflow Steps, or all Workflow Steps of a Job.
Content Converters are not added directly to Jobs, but can be used by Log Filters and Step plugins.