How do metasearch engines work?

Metasearch engines search only sites that are deemed relevant to a particular subject.

Metasearch engines only create an index from which to do an advanced search.

Metasearch engines create guides to the internet organized by topics and subtopics.

Metasearch engines search other search engines ${\displaystyle \underset{\text{t}\text{h}\text{e}\text{r}}{\overset{\phantom{}}{}}}$ than websites.