Plugins add features or functions to SPIP, which might be a set of standardised template files, a modification of existing functionality, creation of new editable database objects,...
They have the advantage of enabling the management of tasks to be carried out when they are installed or uninstalled, activated or deactivated. They can also handle interdependencies with other plugins.
All of the SPIP folders and elements that can be overloaded can be recreated in the folder of a plugin, in the same fashion as is done in your own private "squelettes" folder. The essential difference is the existence of an XML file which describes the plugin, uniformly named