WordPress comes as standard with 2 "post types" - Posts, and Pages. For new users, it's not always clear what the difference is, and where / when you should use each one.
Whilst posts and pages are very similar, in general, the "Post" should be used for blog style posts, and these will show up on your blog or news page automatically once they have been published. By default, posts are shown in chronological order, so older posts will drop down the list (unless you stick them to the top of the blog page).
As standard, if your theme supports it, blog posts will have commenting enabled - so at the bottom of each post there will be a section for your visitors to leave comments, reply to each other, and allow you to reply.
Pages are very similar to posts in terms of how you add them, and how you populate them with content, but they have some distinct differences. Firstly, with a standard WordPress setup, pages will not appear on your blog page, or your archives page, and secondly, on most themes, pages will not have a comments section on them unless you specifically go out of your way to add one.
A page should be used for anything that you would see as static content in your site's structure. Some examples would be an about us page, a static homepage, or a contact us page - the Page option is much better for this type of content than "Posts"
You also cannot set a post as your static homepage or blog page, because they aren't "pages" in the literal sense.
Posts: Should be used for any news, blog, guide, or how-to style content. They will appear on your blog and archive pages, and will as standard be arranged in chronological order
Pages: Should be used for any static content on your website, for example your homepage, an about us page, a contact page, anything which would be accessed frequently and add to your website's structure, a good (but not foolproof) way to decide is, would you put this on your main menu? If you would, it should likely be a page.