WordPress was built as a blogging platform and that still shows, even if its a complete Content Management System in its current version.
Because of that the first thing you will find in your Dashboard menu is the Posts option.
Posts are presented in a chronological time-line.
This means that the latest post will show up first before the rest of the Blog entries.
Posts can be attached to categories; pages can't (unless you use a special Plugin)
In the archive pages there will be posts that are labeled to be part of such a Category or Tag.
You can also have monthly archives and Author Archives, but posted articles overviews are always in a Chronological order.
WordPress Posts are great for adding news items or just new articles you want to share with your website visitors.
It all depends on the purpose of your site if you want to write posts or create pages. Creating fresh posts is not only great for your visitors but also for your search engine rankings as sites like Google, Bing and Yahoo love to see regular updates on a site.
Pages are more static, and that means you can use them any way you want to structure your WordPress website.
Pages are the way to go if you want to Build a Static WordPress website.
There is a great plugin called Nested Pages that can help order your pages and to create new pages.
Pages can also be placed as a sub page to a Main page.
Managing page orders with this Plugin is as simple as dragging and dropping, but don't forget the hit save afterwards.
If your already have pages setup and want to restructure your site, please be careful with moving around those pages. If you place them as sub-pages under other main pages your URL will change. So don't do that or make sure you redirect those old links to the new ones.
“**Important: Changing page structures on live sites may effect SEO and existing inbound links. Limit URL structure changes on live sites by disabling nesting. Sorting within the current nesting structure will still be available. If nesting changes are made to a live site, it may help to add a 301 redirect from the old location to the new one.”
Version 3 of WordPress brought us the Menu option which gives you the option to create special menus with pages and post categories.
To create menu go to Appearance -> Menu. Choose Create a new menu and give the menu a name, like Main Menu or Top menu and save it.
Once the menu is saved your can start adding pages, links and post categories in any order your want. For example, you select the pages you want to add and add them, after that you can drag and drop them into the positions you want to show them.
When choosing Pages to add, select the View All option to also show your Home page link.
WordPress Posts or Pages
If you want to choose between WordPress Posts or Pages keep your website goal in mind.
Just want to create a static business site without news items or a blog? Use pages and create a menu in a way that people can easy navigate to your business offerings.
You can always add that News page or Blog pages later if you want too.
Use Posts for blogging and news items and create a menu with your posting categories so your visitors can get a quick overview of your site topics and navigate to the articles.
You still will need some basic pages like your About page, a Contact page and possible a sitemap page as well.