Although blog posts and pages can be displayed the same way in the front-end of your website, their main difference lays on the way they are archived.
You can format pages and posts the same way since they share the same CSS style that controls your blog theme.
Posts are archived by date (day, month, year) the minute your publish them. You can choose a category or categories for a given post to create a thematic grouping and archiving of your posts.
Pages are saved the very same way posts are but are not tied to any category: blog pages are “uncategorized”.
Pages in a WordPress blog are alike web pages in a traditional web site, that is, the content, topic or subject of a blog page is not opened for comment even if you check the “Allow Comments” box in the page editor section.
Blog Pages also differ from posts in the way the URL is defined depending on your permalinks settings.
Because of this and other reasons a typical blog has just a few pages such as “About” (i.e. http://blogfornoob.blogspot.com) so you can display a pages navigation on your blog sidebar for quick access.
There you have it. In a nutshell, posts can be opened for comments but pages are not.