Robots. The instructions for web "robots" that browse to this page.
Use Global: Use the value set in the Component→Options for this component.
Index, Follow: Index this page and follow the links on this page.
No index, Follow: Do not index this page, but still follow the links on the page. For example, you might do this for a site map page where you want the links to be indexed but you don't want this page to show in search engines.
Index, No follow: Index this page, but do not follow any links on the page. For example, you might want to do this for an events calendar, where you want the page to show in search engines but you do not want to index each event.
No index, no follow: Do not index this page or follow any links on the page.