Posts vs Pages
It's really quite simple to get to grips with the differences between the two.
Posts
This is where you write your articles, news reports, events results and blog entries. Posts are usually timestamped and organised by latest post first. Posts also commonly display the author.
You can add categories and tags to a post. These help organise your content and make it easy for a customer to find the content. To find out more about how and when to use these read our Categories vs Tags guide.
Pages
Pages on the other hand are for more static content i.e. accessible all the time. For example a contact page, or an about page, or maybe a landing page that will contain your latest articles (posts). Pages are generally defined so that they are always accessible from the front page.