Layout Override Files that gives you control over the display of modules or components. Override files are placed in special folders and can be used in place of the standard layout files. Unlike Template Overrides, which override layout files of the same name, Layout Overrides are additional layout files that give you more options and control.
FOSS Acronym for Free or open-source software. Software, like Joomla, that is available to use, copy, study, and change in any way without charge. FOSS software typically uses a special software license, such as GPL, that requires any derivative works to also be free.
API Application programming interface. The published methods for using a set of programs. In Joomla, the API refers to the public methods and fields of all the defined classes, especially ones in the Joomla platform. Because third-party programs rely on the API, it should be changed as infrequently as possible and always with advanced notice.