Extendability of Hippo CMS is achieved by means of a configurable plugin framework. All functionality outside the core is implemented as plugins, which can be extended and customized. New plugins can be written to add functionality. New functionality will typically be implemented as an add-on, consisting of a number of plugins.
Hippo CMS 7 has a modular architecture and plugins can add functionality to either the CMS 7 user interface or to the business logic (i.e. to the augmented repository, where the content is kept and workflow executed). A user interface plugin may add elements to the user interface, change the look and feel or change a functionality. A business logic plugin, i.e. repository plugin, may change workflow and perform data transformations and computations. Combined add-ons contain plugins for the user interface as well as for the repository.
See the related docs block on the right side for further information.