WordPress Post refers to content entries, which is listed in reverse chronological order site widely. You can get it listed in Categories, Recent Posts, and Archives. Also, it is included in RSS feed of the blog. WordPress Page is static and one off content. Specifically, the about page, privacy policy are vivid examples. The page, without tags and categories, is displayed in the sidebar and Pages widget. Namely, if you use Pages widget, then all pages are displayed all the while.