What are Web applications?

They are accessed using a web browsers and Usually interactive. Applications usually give the user info or a result and are made with mixtures of web languages e.g Javascript, HTML, CSS, (Server side PHP). They can have static or dynamic content and are client server based, where the client runs in the browser. Examples: Yahoo Mail, Salesforce CRM, Google Calendar.

What are content management systems?

A system that manages content (data, images etc) and usually database driven. They have a front-end HTML with a back-end database. They have user dashboards/GUI for content manipulation and have security to limit or restrict user engagement. Usually they will have some form of graphical editing tools. Examples: Wordpress, Drupal, Joomla.