Content Management System (CMS) allow managers to control their website's design, to create new content and to update any content in the website.
CMS also improves communication between users, who can now be invited to contribute and share content, based on user roles.
Until recently, when you wanted a website, you also needed a webmaster or programmer, and you still had to pay for their services everytime you wanted to add or update content on you own website.
Today, content management systems build beautiful websites, and let you add or update any content at any time, without any technical background.
If you are building a website, ask for CMS
Have you already decided to go for a CMS ? Drupal is your best choice !