Page- 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/
Post- Posts 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/
Tags- Tags provide a useful way to group related posts together and to quickly tell readers what a post is about. Tags also make it easier for people to find your content. Tags are similar to, but more specific than, categories.Depending on the theme and widgets you have activated, tags can be displayed at the top or bottom of posts, on the individual post view, and/or in the sidebar. You can assign multiple tags per post.
Categories- Categories provide a helpful way to group related posts together, and to quickly tell readers what a post is about. Categories also make it easier for people to find your content. Categories are similar to, but broader than, tags.Depending on the theme and widgets you have activated, categories can be displayed at the top or bottom of posts, on the individual post view, and/or in the sidebar. You can assign multiple categories per post (you must assign at least one), and categories can be organized hierarchically.
Feeds– A feed (often called RSS) is a stream of posts or comments that is updated when new content is published. This is very useful, as it allows other people to monitor your blog, along with other websites they are interested in, and aggregate them together through applications known as feed readers.