Answer:
Indexed pages
Step-by-step explanation:
Search engine optimisation is the way by which websites are improved so that search engines are able to rank their content higher in search results.
Ranking is done by how relevant the website content is to the search query inputted by a user.
Search engines are constantly searching through websites and indexing web pages that meet its requirements for relevant content. This makes up indexed pages from websites.
Organic search are queries inputted by users and not influenced by payed advertisements. They lead to indexing of pages.
This is a good measurement of how effective optimisation of websites is.