A Joomla layout defines markup for a particular output fragment. It can be used by a component view, module or the JLayout system.
Layouts and site templates
A Joomla template provides the overall page shell. A layout handles a narrower area, such as an article card or image. An override replaces a supported standard file, while an alternative layout can be selected separately where the extension supports it.
Customising output
Before changing Joomla markup, identify the view, layout and active template. Check available data and layout selection settings. Creating an arbitrarily named file does not guarantee that it will be used.
Distinguish Joomla layouts, styles and templates. Compare custom files with updated original output during maintenance.