Posts: These are regularly updated individual content pages. They include Ongoing Events, Blogs, Status Updates, etc. They are catalogued by Date, Tag, Category and Author. In M Theater and other WordPress Themes, they can also be used for special content display, such as the home page Slideshow. There could be hundreds or thousands of Posts on a website.
Pages: These consist of content meant to be static. They include Contacts, About pages, Services Offered pages, etc. In many cases, Page names are displayed on the top navigation bar of a website. There are generally a limited number of Pages on a website, although there is no limit to the number of Pages you can create on your website.