Posts and Pages are two ways you can easily get content onto your WordPress site. Depending on the way you want to organize your site, you’ll probably want to think about which format is best for your needs before adding all of your content.
Posts: Items within a feed
Posts are items which will automatically appear in “feeds” on your website, usually with the latest post at the top.
For example, this post that you are reading right now can be found as part of the category feed for Learn WordPress.
You aren’t required to use posts or take advantage of WordPress’s built-in feed capabilities, but most sites can benefit from the feed idea in many ways. For example, you can create your own post types in WordPress to handle anything from event listings to testimonials, to portfolio items which show off your work.
Pages: Constant, unchanging placeholders
Unlike posts, a page is a single, isolated piece of content that will typically not get pulled automatically into any feed areas on your site.
When you add pages to your site, you will also usually need to add them to your navigation menu or to widget in order for them to be visible to your site users.
A typical use of a Page in WordPress would be an “About Us” statement that is a timeless and constant informational section, as opposed to a news update that belongs to a timeline or feed.
Summary
Overall, pages are for “static” or unchanging areas of your site while posts become part of an overall feed, usually showcasing your content in chronological order.