Denotes questions about Magento 2 AfterPlugins. For general questions use "plugin" tag.
Magento 2 (only)
A plugin, or interceptor, is a class that modifies the behavior of public class functions by intercepting a function call and running code before, after, or around that function call. This allows you to substitute or extend the behavior of original, public methods for any class or interface.
Read more about Plugins in the Magento 2 DevDocs.