A collection of Web pages called Website or Web Site, Web pages can contain images, text, videos and audio files etc. A Website can be accessed using web browser by visiting the Index or home page file and from there all related web pages can be accessed.
Web site can be either static or dynamic:
Static website: can be created using HTML and CSS.
Dynamic website: can be created using any programming languages like PHP (Hypertext Processor), .net/asp.net and java etc. embedded with HTML.
CMS (Content Management System) Website.
A Content Management System (CMS) is a software application with graphical user interface with role-based access to manage digital content of a website.
There are a few popular and wildly used free CMSs like: WordPress, Drupal, Magento, Joomla to name a few. CMS is wildly used by small to medium size businesses because it is easy to manage and cost-effective with a lot of free(and paid) ad-ons offered by a large online community.