Plugins are software components that add features to your server, much like a mod.
Unlike mods, however, plugins do not have a whitelist and only run on the server, not on the client.
How to install a Plugin
A list of all approved plugins can be found and downloaded on the torch website
To install a plugin, just put the .zip in the Plugins folder (torch-server\Plugins).
This can be done while the server runs and new plugins/updated plugins you put there will reload on the next server restart.
There are three major plugins developed by the torch team: Essentials, Concealment and Profiler.
You can find community members plugins here : Plugins List
Please reference Plugins/ObsoleteMembers for information on deprecated methods and members.