In WordPress, Posts are treated differently from Pages.

Posts

By default, date and time of creation are a key part of a post. Posts are always considered to be time sensitive. Posts posted during the same time period are group together by WordPress in archives. Posts are classified or grouped together by optional categories and tags. In addition, Posts can have optional excerpts and trackbacks.

Posts are generally considered to be one shot creations where their creation date is the most important factor.

Pages

In WordPress, pages are analogous to the webpages found in a static website. They are permanent in nature and are not time sensitive. Pages can have a parent page or can have an optional hierarchal structure. Further, different pages can be using different page templates.

Pages generally develop over time where the date that they were last updated is considered important.