Plesk Extension
A Plesk extension is a third-party software that adds new functionality to Plesk. The extensions in Plesk are like the Plugins in WordPress. It allows the developers to add functionality to the Plesk panel via PHP, make CSS and JavaScript tweaks and also allows a fine-grained amount of customizations. In Plesk, the extension utility is used in managing the extensions through the command-line interface. It performs a number of operations on Plesk extensions like creating, and registering them, installing extensions to Plesk and other. The following command is used to display the list of currently installed extensions in Plesk.
plesk bin extension -l