The difference between pages and posts is:
There are very key differences between posts and pages in your WordPress blog.
PostsPosts are entries listed in reverse chronological order on the blog home page or on the posts page if you have set one in Settings > Reading. If you have created any sticky posts, those will appear before the other posts. Posts can be found in the Archives, Categories, Recent Posts, and other widgets. Posts are also displayed in the RSS feed of the blog. You can control how many posts are displayed at a time in the Reading Settings. The URL for a post includes the date the post was published like this: http://blogname.wordpress.com/2008/11/30/post-title/
If you want your posts to appear on a page other than your home page, read this: Front Page.
See Posts for more detailed information.
↑ Pages ↑
Pages are static and are not listed by date. Pages do not use tags or categories. An About page is the classic example. Pages can be displayed in the sidebar using the Pages widget, and some themes display pages in tabs at the top of the blog. If you have 50 pages and you use the Pages widget, then all pages will be listed all the time. The URL for a page looks like this: http://blogname.wordpress.com/page-title/
See Pages for more detailed information.
How many can I have?There is no limit on the number of posts or pages you can have.
How do I post to a Page?
All posts will appear on the main posts page, but you can also display specific posts on category pages with our custom menus feature. If you want, you can change the default page for posts to appear by changing Settings -> Reading in the Dashboard. This will likely require changing your Front page as well