Have you written a Jenkins plugin, or helped to maintain one, or are planning to write one? If so, you need to understand where the Pipeline feature might fit into your plugin’s design.
The bare minimum of being “Pipeline-compatible” is that the plugin’s features can be used in a way analogous to their use in traditional Jenkins projects. Learn about the critical APIs that make this possible, and the accompanying restrictions needed due to both the “durability” and greater flexibility of Pipeline builds.
More sophisticated plugins can use Pipeline-specific APIs, mainly to define new “steps”. See the options available and the reasons why you would—or would not—need to add this dependency. Learn the advantages and disadvantages of special DSL additions and libraries.
You will also get an overview of plugin features which do not need to be ported to Pipeline because there is already a way to accomplish the goal without them. This can help you judge whether a new development effort will pay off or whether the time would be better spent documenting a different usage mode.
Whatever implementation choice you make, see how the Jenkins test harnesses can be used to prove smooth operation of the result.