Typically the user will access the content management admin via a logon page, once logged in you will be able to edit pages using a WYSIWYG interface (What You See Is What You Get) this means the way the page appears on the design page is how the page will appear on the live pages of your website. This interface will be very familiar to you if you have previously used Microsoft Word or similar Software.
The CMS will also have a Template assigned which describes how the pages are laid out and contains all the images associated with the design of your website, the template will have been designed and tailored to your needs by a web designer (me). Other generic Templates are available but they may look basic or impersonal and not unique or designed to the theme of your business.
Many additional Modules are available and can be installed onto the CMS if you need your website to do additional tasks such as e-commerce, link to Facebook or Twitter, display a Photo Gallery or create a customised contact form page.
It should be mentioned that other CMS’s are available apart from the main two, Drupal deserves a mention (also available here) but the main two are popular, secure, tried and tested and have an abundance of features and add-ons available as well as a large support community making them a wise choice to manage your website.