The standard Joomla search component, upgraded to work in Joomla 4, along with a set of search plugins and a search module. One for Remository and also search plugins for the usual standard Joomla components. This is not needed for a site that has been upgraded from Joomla 3 to Joomla 4, because the old search component will be carried through. But a Joomla 4 site built from scratch will not have the old search component. Remsearch is a replacement. Please see the article about Remository Search that is in the documentation. at.