From the ‘front end’ or ‘outside’ of a website you cannot tell the difference between a traditional HTML website and CMS website. The differences lie in the ‘back end’ or ‘administrator’ section of your website.
Traditional HTML websites are built and then the files or pages, are uploaded to your web host or server. Changes to the content, menus, links, or images must be made through an HTML editor and the files must be transferred over a protocol such as FTP. This can be difficult for someone who is not familiar with editing HTML or with transferring files to a web server. In many cases a web developer may need to be contacted to make the necessary changes.
A content management system (CMS) is an application that allows for the creation and editing of content as well as for performing other site maintenance. It allows you control over many aspects of your web site such as the text, links, navigation, images and documents. A major advantage of using a CMS is that it requires almost no technical skills or specialized knowledge. You can also change, add or remove content at often as you like and without the assistance of a web developer. Content Management Systems often have plugins or other functionality that allows you to extend the base system to allow for even greater control. Additional software that you may be able to install includes shopping carts and social media integration.
It is often a good idea to determine upfront whether you will want to be able to edit your web site yourself. Make sure to speak with your web developer about your requirements so that he or she knows your requirements and can build the site around a CMS if necessary. Although it is possible to transition an existing HTML site to a CMS driven site it is often easiest to implement the CMS from the start.