In addition to the core features supplied with every orcharhino installation, there are a number of optional plugins that extend the available feature set.
You can see what plugins are installed on your orcharhino on the plugins tab of the system status area. Some of the plugins listed on the about page are developed and maintained as plugins, but actually include core functionality that is always needed on every orcharhino. Such plugins are not really plugins from the user perspective and are not treated as such in this documentation.
There are currently two fully-featured plugin usage guides available which will generally include installation steps, as well as a short description on what the plugin does and how it is used: