"Add To Bookmarks" is usually referring to adding a link/URL to your Web Browser's bookmarks list/folder. This is the old way of managing your bookmarks. Now when you see "Add To Bookmarks," it's referring to one of the "Social Bookmarking" sites, where you, your friends, and several thousands of strangers all post and interconnect their favorite links.
https://addtobookmarks.com/
Widgets