InSpec Plugins are optional software components that extend the capabilities of InSpec. For example, [`inspec-iggy`](https://github.com/inspec/inspec-iggy) is a Plugin project that aims to generate InSpec controls from infrastructure-as-code files. Plugins are distributed as RubyGems, and InSpec manages their installation. InSpec Plugins always begin with the prefix 'inspec-'.
Train Plugins allow InSpec to speak to new kinds of targets (typically new remote targets or APIs, but you could treat the local system in a new way if you wished to). For example, if you wanted to audit a Kubernetes cluster, you might want a transport that can talk to the supervisor API. You would develop a Train Plugin for that, and install it using the InSpec command line. Train Plugins always begin with the prefix 'train-'.
For more details on what the `plugin` command can do, see the [online help](https://www.inspec.io/docs/reference/cli/#plugin), or run `inspec plugin help`.