Solution
Activate the “Wiki Page Home Page” feature. The feature will create those libraries and will also create a wiki page and set it as the home (welcome) page for your site.
Activate SharePoint Server Publishing Feature for Add Page Option in Settings Menu.
A Pages library is a document library that contains all the content pages for a publishing site. A site that has thousands or tens of thousands of pages stored in the Pages library must consider a unique set of issues that relate to managing these pages, and providing navigation between them in a site.
Site Pages library that contains all your pages (including the home page) so as you create new content.
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